506 BOTANICAL GAZETTE [juxe 



the epidermis and the sporangium. The nucellus increases in 

 diameter by anticlinal divisions of both epidermis and sporangium 

 wall. Basal growth takes place also, so that the sporogenous 

 region becomes situated in the focal center of the oval nucellus 

 (figs. 40-42). From this time greater meristematic activity occurs 

 in the peripheral regions contiguous to the line where nucellus and 

 integument meet, resulting in the enlarged base of the nucellus. 

 The tapetal function of that portion of the nucellus immediately 

 surrounding the developing gametophyte, and the digestion of the 

 nucellar tissue in the enlargement of the endosperm have already 

 been described (12). The growing endosperm presses upon and 

 stretches the nucellus so much that at maturity it is but a thin 

 layer surrounding the endosperm. 



A feature of interest is the extent of the freedom of the nucellus 

 from the integument. In the earlier stages of development the 

 two structures are entirely free from one another, a condition which 

 persists until about the time of fertilization. The chalazal region 

 now becomes the center of great meristematic activity, resulting 

 in the development of the aril and the zonal growth of nucellus 

 and integument as a united structure, so that at maturity the 

 freedom of the nucellus from the integument is only partial. 

 Hofmeister's (14) statement that in T. baccata the separation 

 between the " nucleus" (nucellus) and the integument extended 

 entirely to the base was most probably based on young ovules. 

 Freedom of nucellus and integument occurs in Paleozoic seeds 

 belonging to the Cordaitales, such as Cordianthus, and is perhaps a 

 primitive feature retained by most modern gymnosperms only 

 during the early stages in the development of the ovule. That 

 freedom of the two structures should persist longer in some forms 

 than in others is not surprising, and has been regarded as having 

 morphological significance. Taxus, Torreya, and some others are 

 alike in retaining this feature for some time, the relative amount 

 of it being correlated somewhat with the size of the seed, basal 

 growth of the ovule being more extensive in some forms than in 

 others. Oliver (21) has called attention to the basal intercalary 

 growth of the ovule in Torreya, which results in raising both 

 nucellus and integument. He also suggests that the lower portion 



