Orthotropous Ovules Research Articles

Factors Influencing Fruit Setting in the Pecan

1. The pistillate flower of the pecan consists of an orthotropous ovule, surrounded by a single integument. The portion which becomes the shell consists of two carpels, which are transverse on the axis of the inflorescence. The 4-valved husk is developed from the lower portions of the calyx lobes. The flowers are sessile on the peduncle, and are borne in clusters usually of two to six. 2. The pollen tube grows down through the style and ovary wall or integument to the base of the ovule, and returns through the chalaza and nucellus to the embryo sac, fertilization occurring about 4 weeks after pollination. 3. There is a definite drop of young nuts about 4 weeks after the time of pollination, and this drop accounts for over 75 per cent of the seasonal drop. It appears to be due to lack of pollination. 4. The varieties tested show no evidence of self-incompatibility or inter-incompatibility. Good sets of fruit were obtained from any variety of pollen available when the flowers were receptive. 5. The period o...

Studies in Araceae

In the fall of i906 the writer enjoyed the privilege of examining the extensive collection of tropical aroids in the greenhouses of the New York Botanical Gardens, and of collecting material for an investigation of the embryo sac and embryo. Among other species, Nephthytis Gravenreuthii was selected for this purpose. A considerable amount of material was obtained, illustrating stages from the archesporium to the mature embryo. OVARY.-The genus is characterized by a single simple carpel which shows a tendency toward a slightly unsymmetrical development, the stylar canal never being in the axis of the carpel (fig. 2). The carpel is short and thick, the stylar canal very short, funnelshaped, and lined with viscid conducting cells. On the interior of the carpel the conducting cells reach a considerable length and come in contact with the ovule on all sides, sometimes reaching quite to the micropyle. OVULE.-The ovary contains a single, basal, anatropous, cauline ovule. Probably the single, basal, orthotropous ovule is the most primitive kind, and in Arisaema we find an orthotropous ovule, but there are typically four ovules; and while they are cauline in origin they occur as lateral outgrowths of a suppressed placenta, the illdefined point of the placenta representing the axis of the flower. The single axial ovule, even though it be anatropous, is no doubt a simpler type than this; and when we compare it with such a form as Dieffenbachia, in which each ovule, arising from the partially suppressed placenta, is surrounded by a separate carpel, its primitive character becomes yet more apparent. In general, the ovule of the species now under discussion is peculiar for its massive integuments and for the poor development of the nucellus. The latter consists at first of a single row of cells sur35] [Botanical Gazette, vol. 46

Embryogeny of Arisaema Triphyllum

Although the dioecious character of Arisaema would indicate for it a very low place among the aroid genera, other characteristics do not entirely bear out this view. The erect and orthotropous ovule, it is true, seems to indicate it as a primitive form, but the fact that there are four ovules (typically) in each ovary, and that their basal origin is apparent only, since they are in reality lateral outgrowths of the suppressed axis, seems to prove it a more highly specialized type than Aglaonema, Nephthytis, and Spathicarpa, in all of which each carpel contains a single basal ovule. This view is confirmed if we consider the variations in the number and arrangement of the nuclei in Nephthytis and Aglaonema (Campbell, l. c.) as indicating their primitive character. The development of the embryo sac in Arisaema corresponds to the usual type found in other angiosperms, and gives no hint of its possible affinities with lower forms. On the other hand, the early presence of a number of sporogenous cells in the nu...