160 A. H. Graves, 



The anatomy of the seedUng 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 

 b}^ it from the innermost cell. 



