4i8 



GYMNOSPERMS 



alcd into a stony layer in the middle, with a fleshy layer on each side. 

 Such a statement involves the assumption that the nucellus and in- 

 tegument are united, except at the "free" part of the nucellus, an 

 assumption originating from the fact that some very ancient seeds 

 have the integument and nucellus free from each other throughout. 

 In Ciicluni, the outer integument becomes differentiated into an 



Fig. 390. — Gnetinn gnemo)i: Typical ovulate strobili collected in the Philippines. 

 Three young strobili, like the one from which fig. 388 was made, are shown at the left. 

 The others show ovules in various stages of development; about natural size. — From a 

 negative by Dr. W. J. G. Land. 



inner stony layer and an outer fleshy layer. In an attempt to unify, 

 some have regarded the outer integument as having been differenti- 

 ated from the inner during phylogeny. They were probably never 

 more united during phylogeny than they are now in ontogeny. In 

 Lyginoplcris, the outer layer of the integument becomes stony, while 

 the cupule serves as an outer fleshy layer. Physiologically, the three 

 layers are efficient during the development of the seed and, at ma- 

 turity, they are protective. Their function is as uniform as that of 

 tendrils, and their homology may be as various. 



The archesporium is hypodermal, dividing into a primary sporog- 



