Monocotyledonous Group Research Articles

AGAIN: THE GROWTH HABIT OF THE EARLY ANGIOSPERMS

The question of the putative growth habit of early angiospermous plants, recently brought to the fore again by Stebbins (1965), is not a simple problem, it being complicated by, e.g., the alternative hypotheses of a single or a multiple descent of the Flowering Plants. A reconsideration based upon palaeobotanic, comparative morphological, and other evidence reveals that, in contradistinction to current views, the probable growth habit of pre- and proto-angiosperms was not of a single (uniform) type, but varied and included nearly all types exhibited by the various, recent dicotyledonous and monocotyledonous groups except the truly therophytic life form. Among the arborescent life forms represented at an early stage, the lofty dicotyledonous tree habit, though presumably present, was comparatively rare.

THE SYSTEM OF THE ORCHIDALES

After an enumeration of the most characteristic features of the Orchidales, the affinities between this order and other monocotyledonous groups are discussed. The Orchidales must be placed in the system immediately after the Commelinales, chiefly on account of their androecial morphology. For reasons explained in the present paper the Orchidales are subdivided into three families, viz. the Apostasiaceae, Cypripediaceae and Orchidaceae. The principal differences between these families are shown in the form of tables. In the Orchidaceae two subfamilies are recognised and amply circumscribed, viz., the Orchidoideae and the Epidendroideae, the latter again being subdivided into the two contribes Neottianthae and Epidendranthae. The androecial morphology is discussed in detail in connection with atavistically developed stamens, with the presence of staminodes (or supernumerary stamens) and with the floral morphology of certain taxa. The auricles are not regarded as staminodes because they persist in flowers with supernumerary (atavistically re-appeared) stamens and also because they lack vascular bundles. The gynostemial wings in some Australian genera (Diuris, Prasophyllum, and other ones) are considered to be of androecial derivation The less conspicuously winged but vascularised margins of the gynostemium of many Epidendroideae likewise represent androecial elements incorporated in the column. The suggestion, made by E. Nelson, that the lip is the phylogenetic derivative (the homologue) of the ‘missing’ stamens A2, a3 and A3 (which implies that the median petal has disappeared), is rejected, primarily because Nelson's arguments are based on the morphology of the labellum in the highly specialised genus Ophrys. The floral morphology of Neuwiedia and of some species of Herminium, on the contrary, is indicative of the petaloid nature of the lip which, accordingly, represents the median petal. The vascular anatomy of the orchid flower does not provide arguments in favour of the suggestion made by Lindley (later taken up by Darwin) that the ‘missing’ stamens A2 and A3 are incorporated in the gynostemium. The orchidalean ovary appears to be compounded of six parts, viz. three broad hyposepalous zones alternating with as many hypopetalous elements bearing the (double) laminal placentae on their inner face. This is considered to be a convergence towards the condition prevailing in Rhoeadales (Brassicales) (genus Eschscholzia etc.). In the Orchidoideae the stigma is locally differentiated into viscid discs which are situated distally of the lateral stigmatic lobes, and the median stigmatic lobe is functional in several genera, but in the Epidendroideae the median stigmatic lobe is apically transformed into a mucilaginous substance or a viscid disc, or it is completely replaced by a viscidium. In Stereosandra the viscidial element is a derivative of the anther.

Orcein staining and the study of the effect of chemicals on chromosomes.

Plant materials of both dicotyledonous and monocotyledonous groups were subjected to treatment with alloxan followed by coumarin, phenols, oxyquinoline etc. for 3 to 4 hours. Root tips were then heated in an orcein-acid mixture for 10 to 40 seconds and studied after mounting in 1% orcein. Clear metaphase plates were obtained after 10 seconds of heating, whereas after 20 and 30 seconds considerable erosion and fragmentation respectively were recorded. Complete loss of stainability resulted after heating for 40 seconds. Fragmentation is caused only by orcein under heat conditions. This is demonstrated by control series checking all variables. Pretreatment with the chemicals stated is of absolute necessity for fragmentation. It is suggested that this pretreatment causes depolymerisation of DNA and lability of nucleoprotein linkage at certain segments from which the DNA becomes detached during subsequent heating. Of all the chemicals tested for pretreatment effects, marked positive results were obtained with alloxan (1 hour) followed by coumarin (2 hours at 16–20 ° C.). Phenols also gave positive results. The other chemicals tried need slightly longer time of treatment for fragment induction.

Recent Work on the Systematic Anatomy of the Monocotyledons (With Special Reference to Investigations at the Jodrell Laboratory at Kew)

After the publication in 1950, of the 2 volumes by Metcalfe and Chalk entitled 'Anatomy of the Dicotyledons ', it was felt that a reference book dealing with the anatomy of the Monocotyledons was badly needed. Research, which it is hoped will ultimately lead to the publication of a work of reference on this subject, is now one of the most important tasks on which the staff of the Jodrell Laboratory are engaged. Before embarking on this great undertaking, the matter was discussed by correspondence with Dr. F. J. Meyer, who, from 1928-1933, was, in collaboration with the late Professor Solereder, producing, in parts, a reference work entitled ' Systematische Anatomie der Monokotylen '. Dr. Meyer informed me, however, that owing to various difficulties, including those of publication, he would be unable to finish the work. Although nobody, apart from Solereder and Meyer, has attempted to make a comprehensive survey of the anatomy of the Monocotyledons, numerous accounts of investigations dealing with restricted groups of Monocotyledons have been published, particularly by French and German investigators at the end of the last and at the beginning of the present century. More recently the investigations by Cheadle and his colleagues in the U.S.A. concerning the structure of Monocotyledons in relation to their phylogeny has aroused fresh interest, and studies by agrostologists, particularly those by Prat, have reemphasised the importance of comparative anatomy in the taxonomy of the Gramineae. Professor Kaul in India has for many years been engaged in studying the structure of palm trunks in relation to their classification ; and he has secured most interesting results which are as yet not widely known because they remain unpublished. Our first task in preparing a book on the comparative anatomy of the Monocotyledons was to index the great wealth of anatomical literature, scattered as it is in many different journals, on a taxonomic basis. This has now largely been done thanks to the valuable assistance of Miss E. Slatter, working at Kew, where she prepared a most important card index to the literature. This index is proving invaluable not only for our own researches, but to botanists outside Kew who have wanted to know what literature there is dealing with the anatomy of the plants in which they are specially interested.

Leaves of the Farinosae

Previous articleNext article FreeLeaves of the FarinosaeAgnes ArberAgnes Arber Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Volume 74, Number 1Sep., 1922 Article DOIhttps://doi.org/10.1086/333056 Views: 33Total views on this site Citations: 11Citations are reported from Crossref Journal History This article was published in the Botanical Gazette (1876-1991), which is continued by International Journal of Plant Sciences (1992-present). PDF download Crossref reports the following articles citing this article:Sabina Donadío, Walter Till, Raúl Pozner, Michael H J Barfuss, Liliana M Giussani, Julian R Starr Phylogenetic relationships and evolutionary trends in Tillandsia subgenus Diaphoranthema and xerophytic species of subgenus Phytarrhiza (Bromeliaceae: Tillandsioideae), Botanical Journal of the Linnean Society 200, no.44 (Jul 2022): 541–562.https://doi.org/10.1093/botlinnean/boac020Dastan M. Khoshnaw, Adriana L.R. Oliveira, Ashwini M. Darshetkar, Ritesh Kumar Choudhary Leaf anatomy of Eriocaulon (Eriocaulaceae, Poales) species reveals a correlation between life form, anatomical features and life cycle, Flora 288 (Mar 2022): 152021.https://doi.org/10.1016/j.flora.2022.152021Dmitry D. Sokoloff, Margarita V. Remizowa, Matthew D. Barrett, John G. Conran, Paula J. Rudall Morphological diversity and evolution of Centrolepidaceae (Poales), a species-poor clade with diverse body plans and developmental patterns, American Journal of Botany 102, no.88 (Aug 2015): 1219–1249.https://doi.org/10.3732/ajb.1400434Renata Callegari Ferrari, Vera Lucia Scatena, Aline Oriani Leaf and inflorescence peduncle anatomy: a contribution to the taxonomy of Rapateaceae, Plant Systematics and Evolution 300, no.77 (Feb 2014): 1579–1590.https://doi.org/10.1007/s00606-014-0984-1M. G. SAJO, P. J. RUDALL Systematic vegetative anatomy and ensiform leaf development in Xyris (Xyridaceae), Botanical Journal of the Linnean Society 130, no.22 (Jun 2008): 171–182.https://doi.org/10.1111/j.1095-8339.1999.tb00517.xD. W. Stevenson, M. Colella, B. Boom Rapateaceae, (Jan 1998): 415–424.https://doi.org/10.1007/978-3-662-03531-3_40R. Kral Xyridaceae, (Jan 1998): 461–469.https://doi.org/10.1007/978-3-662-03531-3_47H.-J. Tillich Development and Organization, (Jan 1998): 1–19.https://doi.org/10.1007/978-3-662-03533-7_1Stephanie Splett, Wilhelm Barthlott, Thomas Stützel, Mariluza Araujo Granja E Barros Leaf anatomy of Brazilian Eriocaulaceae and its diagnostic significance, Flora 188 (Jan 1993): 399–411.https://doi.org/10.1016/S0367-2530(17)32290-9 Agnes Arber Leaves of Triglochin, Botanical Gazette 77, no.11 (Oct 2015): 50–62.https://doi.org/10.1086/333280 Agnes Arber Leaves of the Gramineae, Botanical Gazette 76, no.44 (Oct 2015): 374–388.https://doi.org/10.1086/333269

I. On the organization of the fossil plants of the coal-measures. —Part VII. Myelopteris, psaronius, and kaloxylon

The existence or non-existence of the remains of Palms in the Carboniferous strata has long been a debated geological question. Accepting the determinations of Corda as announced in his ‘Flora der Vorwelt,’ many geologists admitted these true endogens into their lists of Carboniferous plants. Cotta had figured, in his ‘Dendrolithen,’ three very anomalous stems, under the names of Medullosa porosa , Stellata , and elegans . Corda, in his 'Flora der Vorwelt,’ subsequently figured two stems from Carboniferous strata obviously allied to one, at least, of Cotta’s types, under the names of Palmacites carbonigerus and P. leptoxylon , which he placed in the class of Palms. Cotta’s figures of Medullosa elegans are very misleading, though they are not very unlike the specimens which he probably described. Some specimens now in the British Museum which came direct from Cotta, and for having my attention drawn to which I am indebted to my friend Mr. Carruthers, exhibit a remarkable areolation when cut transversely. This areolation Cotta has not only copied but exaggerated; hence the peculiar aspects of his figures 1 & 8 of his Medullosa elegans ; it certainly is not a constant and normal feature, but the result of some change produced subsequent to the life of the plant—most probably a consequence of partial desiccation of the stem. Cotta’s drawings of the cortical layer also are very misleading; hence it is very unsafe to accept his delineations apart from the study of his specimens, some of which, I fear, are no longer to be found. The consequence is that two of his species, M. stellata and M. porosa , remain too obscure to be relied upon without further evidence than Cotta has handed down to us. The first to throw doubt upon the Monocotyledonous character of these plants was M. Brongniart in his ‘Tableau des genres de Végétaux fossiles,’ published in 1849, extracted from the ‘Dictionnaire Universel d’Histoire Naturelle.’ He identified Cotta’s Medullosa elegans with some important plants not uncommon in the Carboniferous beds of Autun; and whilst he thought that these specimens displayed a structure analogous to that of some Monocotyledons, especially of Draœena, he adds, “il y ait des différences fort essentielles et qui rendent très-difficile d’établir des rapports entre ces fossiles et les végétaux vivants”*. M. Brongniart consequently proposed to make Cotta’s Medullosa elgans the type of a distinct genus under the name of At a later page of his work (p. 97) he further gives a list of fourteen Carboniferous Monocotyledons, in which he includes seven species of Trigonocarpum , his proposed genus Myeloxylon , and the Palmacites carbonigerus and leptoxylon of Corda, at the same time declaring that all these supposed Carboniferous Monocotyledons are “ très-douteuses et imparfaitement connues.” At p. 89 of his work he retains Corda’s genus Palmacites , but remarks respecting the two species from the Carboniferous strata, viz. P. carbonigerus and leptoxylon , that they appear to be distinct from the Palms, and probably also from the group of Monocotyledons, thinking them analogous to the Medullosa elegans of Cotta, adding, in reference to the latter plant, “ qui n’est certainement pas un palmier.”