1909] CHAMBERLAIN— SPERMATOGENESIS IN DIOON 235 



Dorety, Sister Helen Angela, Vascular an; 

 Microcycas calocoma. Bot. Gazette 47: 139-147 



Thiessen 



Bot. 



23-29 



EXPLANATION OF PLATES XV-XVIII 



Figs, i, 2. — In text. 



PLATE xv 



pidermi 



Fig. 3. — Transverse section of a young microsporophyll, showing son, s, 

 mucilage ducts, m, and vascular bundles, 6. Xio. 



Fig. 4. — Two microsporangia of sorus. X55. 



Fig. 5. — Section of a part of the microsporangiun 

 layers, tapetum, and some sporogenous tissue. X250. 



Fig. 6.— Microspore, Aug. 14, 1905. X1260. 



Fig. 7.— Microspore showing the prothallial cell, p, generative cell, g, and 

 tube cell, L X1260. 



Fig. 8. 



rm 



Fig. 9.— Pollen tube somewhat later. Oct. 1, 1907. X1260. 



all, ft. Oct. 21, 1907. Xiooo. 



rm 



f ^r m r ^ ^^ ^"^ ^"^ ^^ » 



Fig. ii.— A later stage; black granules and gray bodies in the cytoplasm of 



the body cell. Xiooo. 



Fig. 



12. 



fig. 11. Xiooo. 



Fig. 13 —Body cell showing black granules. Oct. 23, 1907. X1890. 



Fig. i 4 —Body cell with black granules and gray bodies. Oct. 23, i9°7- 

 X1890. 



Fig. 15.— Beginning of radiations about the blepharoplasts. Oct. 30, 1007. 

 X945- 



Fig. 16.— The blepharoplasts and radiations of the previous figures. X 1800. 



PLATE XVI 



ro 



, FlG - ^--Blepharoplast with radiations and gray bodies, gb; the figure shows 



* lveolar structure of the cytoplasm. X 1890. 



riG. i8.-Pollen tube structures with gray bodies on the radiations sur- 

 unding the blepharoplasts. Nov. 20, 1006. X630. 



Hg. i 9 .-General view of nucellus at stage shown in fig. 18, with pollen 

 tubes and pollen chamber. X30. 



Fig. 2o.-Blepharoplast with gray bodies on the radiations. Nov. 27, 1907. 

 A1590. 



Fig. 



1 —Later stage of blepharoplast and radiations. X 1890 



Fig. 22 ._ Stiu later stage X945 



len h 23 "~~ View of nucellus just before the division of the body cell; the pol- 

 c amber has extended entirely through the nucellus. X8 



