160 A. H. Graves, 
The anatomy of the seedling corresponds in the main to that of 
the mature plant. The central vascular area in the stem is thus 
essentially the same as in the older plant, so that no ancestral 
characters were detected in the vascular system in this young stage. 
SUMMARY OF PARTS 
ON REPRODUCTIVE ORGANS, EMBRYO, &c. 
Flower. The inflorescence is spadix-like, and even a small spathe 
is present, the latter structure having almost entirely escaped the 
notice of investigators. 
The small scaly outgrowths from! the anther-connective probably 
represent reduced floral leaves, judging from the analogy of Pota- 
mogeton, and from the fact that the flower of Ruppia is evidently 
a reduced one. 
The two flowers of the spadix arise laterally from the vegetative 
cone; they develop practically together in point of time, and the 
anthers precede the pistils in development. 
Microsporangium. Appearances indicate that the archesporial 
initials in the microsporangium are a comparatively large group of 
cells which originate simultaneously both in plerome and periblem. 
A plate of sporogenous cells becomes differentiated to form the 
future septum dividing the two sacs of the theca. 
The tapetum is evidently derived from the sporogenous cells. 
The sporophytic number of chromosomes was definitely ascer- 
tained to be sixteen. 
Megasporangium. The megasporangium arises from a hypo- 
dermal cell in the usual way. Generally one layer of parietal cells 
is formed. 
An interesting case was found of two megaspore mother-cells in 
one megasporangium, a condition little known among monocotyle- 
dons. 
Female Gametophyte. Eight chromosomes appear in the first 
reduction division, and probably in the succeeding ones. 
A double megaspore mother-cell was found, which had in each 
case divided into two daughter-cells. 
The four potential megaspores are oriented in such a way that 
the two outer cells are in contact with the third cell, but separated 
by it from the innermost cell. 
