358 



MORPHOLOGY OF THE ANGIOSPERMS 



characterize some parasites, such as Orohanche, and some saprophytes 

 — Monotropa, Pijrola, Bartonm; these embryos are probably reduction 

 types. In some aquatic taxa, such as HijdrocJmris and Ruppia, both 

 endosperm and scutellum appear to have been lost; in the ancestral 

 stock of others, such as Zosfera and Halophila, probably no endo- 

 sperm and no absorbing cotyledon tip were present. 



Fig. 135. Various forms of simple monocotyledon embryos; A, B, E, F, with endo- 

 sperm; C, D, without endosperm, c, cotyledon; h, hypocotyl; p, phimule; r, root. 

 A, Arum oricntalc; B, Carex livida; C, Biitotinis umhcllatus; D, Alisma Plantago; 

 E, Sparganium ramosuni; F, Sagittaria sagittac folia. (After Tschirch.) 



The simple embryo of such monocotyledonous families as the 

 Alismataceae, Butomaceae, and Scheuchzeriaceae has been considered 

 reduced, but this is undoubtedly a primitive embryo. It is cylindrical 

 and has little differentiation of organs. The sheathing cotyledon is 

 cylindrical and seemingly terminal; the root is weakly developed; the 

 plumule is also weakly developed and enclosed within the sheathing 

 base of the cotyledon ( Fig. 135C, D ) . 



"Monocotyledony" in the Dicotyledons. Stages in the reduction of one 

 of an ancestral pair of cotyledons, modified in function, are seen occa- 



