Abortive Spores Research Articles

A system for the study of meiotic non-disjunction using Sordaria bervicolis

Abstract A system is described for the study of abnormal chromosome segregation in Sordaria brevicolis . The system utilizes two complementing alleles of the b 1 locus on linkage group II. Abnormal asci containing black disomic ascospores were detected which fall into two main categories. (a) Non disjunctional asci in which the disomic spores were present together with an equal number of abortive (nullosomic) spores and (b) asci in which an extra replication of the chromosomes had occurred resulting in pseudo-wild types being formed without accompanying spore abortion. Calculations indicate that the non-disjunction frequencies at the first and second divisions of meiosis are 4.25×10 −4 and 4.35×10 −4 respectively. It is suggested that the system is potentially a valuable one both for the study of meiotic non-disjunction and other causes of aneuploidy.

ACHLAMYDOCARPON VARIUS COMB. NOV.: MORPHOLOGY AND REPRODUCTIVE BIOLOGY

Structurally preserved arborescent lycopsid fructifications are described from Pennsylvanian age strata in eastern Kentucky and southern Illinois. Achlamydocarpon varius comb. nov. is the name proposed for these cones and previously reported isolated megasporophylls described as Lepidostrobophyllum varius. The specimens range up to 3.5 cm long and represent cone apices. Megasporophylls are spirally arranged and attached to the cone axis at an acute angle. Megasporangia are large with a wall two cell layers thick. Each sporangium contains one large, presumably functional megaspore, and three smaller, abortive megaspores. Functional and abortive spores possess a prominent apical tuft (massa) that covers up to one‐third of the proximal surface of the spore. Sporoderm ultrastructure is detailed together with a comparison of morphologically similar sporae dispersae megaspores. The possible function of the megaspore massa is discussed as it relates to the reproductive biology of the cone.

12.—Further Observations on some Lower Carboniferous Seeds and Cupules

SynopsisTwenty-eight specimens of the seed genusDolichospermahave been examined. Fourteen are assigned toD. sexangulatumLong; these possess six or seven integumental lobes which extend apically as free tentacles equal in length to the seed body except when damaged or broken off. Fourteen other specimens are namedD. pentagonumsp. nov. These are smaller and usually have five integumental lobes (less commonly six or seven). Long apical tentacles have not been seen in this species.Evidence is adduced thatAnasperma burnenseLong is the mature prothallial seed developed from the ovuleEurystoma trigonaLong.Eurystoma angulareLong sometimes possesses five integumental lobes and the free apical lobes vary in length.Compressed megaspores macerated from cupules ofStamnostoma huttonenseLong sometimes have three abortive spores in a compact group at the apex.Ovules ofEccroustosperma langtonenseLong were borne in small bunches (probably pendent) on short pedicels; one specimen of this seed shows three well-developed separate abortive spores around the apex of the functional megaspore.The cupule ofCalathospermum fimbriatumBarnard shows a structure suggesting that it may have evolved from a pair of cupules. Twelve to fourteen ovules were sometimes formed in the entire cupule though most of these were probably abortive.Some possible seed embryos are described and discussed, and an outline classification of seeds in the order Lagenostomales is proposed.

A Newly Recognized Gleichenia Hybrid from Cuba

While preparing a revision of the Gleichenia family for the Cuban fern flora, I found a species that I think is a hybrid, for all specimens of it that I have examined appear to be sterile, with few sporangia and abortive spores. This species was first described by Maxon as Dicranopteris leonis. In the arrangement of the Gleicheniaceae made by Holttum (1957), it belongs in Gleichenia subg. Mertensia (Willd.) Holttum (see also Holttum, 1973). I postulate that the parents of this hybrid are Gleichenia bifida and G. palmata. The nomenclature and distribution of these species are as follows:

SPORE SIZE IN THE GENUS EQUTSETUM

SummaryNo trace of morphological heterospory has been found in the genus Equisetum. Reports that sex may be altered by environmental conditions indicates that it is not determined by genotypic or physiological properties of the spores. Spore size is extremely dependent on viability, maturity and mounting medium, but within each species all the viable spores are spherical, bright green and vary little in size. Slight subgeneric differences exist in spore size but there is great overlap between all species rendering the spores of little use taxonomically. Colourless abortive spores are found in the two hybrids E.×moorei and E.×trachyodon and also in E. telmateia and E. palustre var. polystachyum. Of common occurrence in E. hyemale, E. ramosissimum and E. laevigatum are small, discoloured, misshapen spores which will not germinate. Considerations of the phenology of these species in relation to experiments on storage of ripe cones indicate that these spores were at one time mature and viable but had subsequently died. In E. variegatum and E. scirpoides large variations were observed between cones, in spore size and germination. This was due to the ripe cones containing variable proportions of mature and immature spores.

The Spore of Oxymitra Androgyna

The mature spore of Oxymitra androgyna, as removed from the capsule of the sporophyte, is very opaque and blackish in color. It is either angular or round depending upon the aspect from which it is observed. From the lateral view, it is oval and angular, the angularity supplemented by the projecting, anastomosing ridges. The full inner face view and outer face view are usually round but may be oval to subangular. In full outer or inner face view, the ridge next to the three inner faces appears somewhat like a narrow wing, and probably could be interpreted as such were it not for the intersections between areolae having elevated, flange-like projections. Areolae varied a great deal in size, so much so, that this measurement was of little value. The range in spore size found to be greater than indicated by either Frye and Clark 1937, or Howe 1914,-125 microns to 175 microns in diameter. Over 60 spores were measured and almost every capsule had a few underdeveloped or abortive spores. Since illustrations in the literature on this species seem to be few, and since the material at the author's disposal was in prime condition, Figures 5 and 6 were added to this paper to show the disposition of several involucres in the median groove from the dorsal aspect, and to show the lateral view of the involucres. Spore masses of each sporophyte were easily obtained by breaking off the upper one-third of the involucre, and digging or shaking the spores out into a drop of water on a slide. The spores used for study, were bleached in 50% commercial chlorox solution, so that they might be observed more critically. This became a very useful technique, as not all spores on a given slide bleached at the same rate. As a consequence, the bleaching was allowed to proceed to the point where all degrees of bleaching could be ascertained. Hence the spore mass, from a given capsule, was dehydrated in 954% and 100% alcohol, followed by pure xylene. Mounted in synthetic resin or balsam, the permanently prepared slide showed the maximum possibilities in range of density, for observation of the characteristics of the spore wall. From such bleached and prepared assemblage of spores, the following description was compiled: Spores angular, sub-angular, oval to round; projections few, compared with the number of intersecting angles of the areolae;

A Comparison of the Basal Scales and Indusia of Dryopteris Goldiana X marginalis with Those of Its Parent Species

The hybrid D. Goldiana x marginalis was described by Dowell as being intermediate between its alleged parents in all characteristics. These included general habit, appearance, color and position of the sori. The description was general and based largely upon gross characters. Benedict (1909) pointed out that although the D. cristata x marginalis hybrid which he described was intermediate in character, not all plants were intermediate to the same extent, some showing greater resemblance to one parent species, and some to the other. Fern hybrids have also been found to be sterile and to have a tendency to produce abnormal or abortive spores. In October of 1935, Dr. Benedict collected about 80 specimens of D. Goldiana x marginalis as well as twenty of each of the parent species. They were found growing in the same locality near Springdale, New Jersey. These leaves were pressed and constituted the material used in the present study. It was undertaken to study the hybrid in comparison with its parent species, particularly with regard to the basal scales and indusia, in order to determine the possibility of diagnostic characters in these structures, and upon what basis they might be differ55