Johnson : Development of Saururus cernuus L 371 



digestion of the perisperm is as yet uncertain, but soon after the 

 embryo pushes out of the seed the endosperm cells begin to lose 

 their contents and do not appear like actively secreting cells. 



The epidermal cells of the tips of the cotyledons have very 

 dense contents and retain this character as long as they remain 

 in the seed. On the surface of the cotyledons, at the tip, while 

 they are still imbedded in the endosperm far from the light, and 

 before chloroplasts are visible in the cells of this region, structures 

 like typical stomata are formed abundantly. These stomata \>r 

 stoma-like structures seem more abundant and more widely open 

 at the very tip than elsewhere on the cotyledons. This fact sug- 

 gests their possible connection with the absorption of food material. 

 This has, however, not yet been proven. 



Of the older seedling, after the empty carpel drops off, I need 



say here only that the first leaf from the plumule expands during 

 the fourth or fifth week, and the second soon follows. In seed- 

 lings of seven or eight weeks the cotyledons cease growth, at a 

 length of about four millimeters ; the two stem leaves at this time 

 assume nearly the typical cordate form of the mature leaf. 



Conclusion 



I have elsewhere stated that I failed to find in the development 

 of the embryo-sac of Peperomia any essential primitive features, 

 and the present study of the related genus Saururus has failed in 

 a similar manner, it seems to me, to indicate this plant as especially 

 primitive. The origin of the parts of the flower and the develop- 

 ment and structure of the mature embryo-sac are essentially as 

 found generally in the Angiosperms. The immediate formation of 

 cell walls in the endosperm occurs, as Hofmeister has shown, in 

 more than twenty different families of this group. The occurrence 

 of further cell walls in but one of the first two endosperm cells he 

 has also shown to be a not infrequent phenomenon. Thus Asarum, 

 Nymphaea, Plant ago, the Campanulaceae, Labiatae, etc., resemble 

 Saururus in forming cellular endosperm in only the upper of the 

 first two endosperm cells ; while in Catalpa, Acanthus, and other 

 forms, it is formed in the lower cell of the pair. 



Again the slightly developed embryo and the small amount of 

 endosperm in the ripe seed, are found not only in the Piperaceae, 

 but in such distantly related forms as Nuphar, Brascnia and other 



