126 



MORPHOLOGY OF GYMNOSPERMS 



of Zamia, which are less than 3 mm. in length. The color is as 

 various as the size, white, creamy, pink, and various shades of red 

 predominating. Within the same species there is not nearly so much 



variation in color of ovules as 

 in size. Some ovules are densely 

 hairy, as those of Cycas revoluta; 

 while others, as those of Dioon, 

 are perfectly smooth. The general 

 topography of the ovule, which 

 is fairly well known in all the 

 genera, is shown in fig. 117. 



Important among the earlier 

 contributions are those of 

 Warming (8, 9) on Cycas in 1877 

 and 1879, and of Treub (ii, 13) 

 on Ceratozamia and Zamia in 

 1881 and 1884. Later, Wors- 

 DELL (270) paid particular atten- 

 tion to the anatomy of the sporo- 

 phylls of most of the genera. 

 Lang (22) studied several stages 

 in the development of the ovule 

 of Stangeria, and Oliver (36) 

 made a comparative study of the 

 ovules of the older gymnosperms. 

 In 1904 Matte (40) and Miss 

 St OPES (42) published inde- 

 pendently and almost simul- 

 taneously very comprehensive 

 accounts of the vascular anatomy 

 of the sporophylls and ovules 

 of all the genera. Matte's 

 account treats of the entire vas- 

 cular structure of the Cycadales, while Miss Stopes deals particu- 

 larly with the ovules, and includes a discussion of the integument as 

 well as of the vascular system. In 1906 Chamberlain (46) described 

 the ovule of Dioon edule, paying particular attention to the structure 

 of the integument and nucellus. 



Fig. 117. — Dioon edule: longitudinal 

 section of ovule after pollination, but 

 about three months before fertilization: 

 a, abscission layer; e, endosperm; i, 

 inner fleshy layer (between i and ») ; ib, 

 bundle of inner vascular system; m, micro- 

 pyle; n, free portion of nucellus; o, outer 

 fleshy layer of integument; oh, bundle of 

 outer fleshy layer; p, basal papilla; s, 

 stony layer of integument; X2. — After 

 Chambeklain (46). 



