CYCADALES 



23 



elusion; Treub ^* in 1884 stated positively that there is no 

 such cell in Gycas circinalis. Until Ikeno's demonstration in 

 1896, therefore, the absence of such a cell in the Cycads was 

 generally accepted. 



It is important to note that the development of a group of 

 archegonia checks the growth of the vegetative tissue of the 

 gametophyte in that region, and the adjacent regions continu- 

 ing to grow, the archegonial region is left at the bottom of a pit- 

 like depression, which may be called the archegonial chamber, 

 or " endosperm cavity," as Warming has called it. This cham- 

 ber is full of liquid during fertilization, and at the bottom of 

 it the necks of the archegonia open (Fig. 18). Occasionally two 

 of these chambers have been observed, each with its group of 

 archegonia. 



THE MALE GAMETOPHYTE 



The male gametophyte begins with the reduction division of 

 the spore mother cell, which seems to have received no special 

 attention in Cycads. The organization of 

 the tetrad by successive division, accom- 

 panied by a peculiar chambering of the 

 mother cell, has been described in detail by 

 Juranyi ^ for C'eratozamia longifolia, and 

 by Treub ^^ for Zamia muricata (Fig. 21). 

 With the appearance of the nuclear plate 

 in the first division, a ring of thickening 

 develops upon the outer surface of the wall 

 of the mother cell in the plane of the plate. 

 Proceeding from this ring of thickening, 

 a heavy wall develops between the two 

 daughter cells. Juranyi thought that the 

 nuclear plate disappears, and that the heavy 

 wall is formed by growth at the free inner 

 edge of the ring. Treub dissents from this 

 view, and, although he could not demon- 

 strate the fact on account of the abundant 

 starch grains, thinks that the nuclear plate 

 persists and gradually thickens, the thick- 

 ening proceeding from the peripheral ring toward the center. 

 The latter view seems to be the more reasonable one. The two 

 3 



c 



Fig. 21. — Zamia muri- 

 cata ; successive stages 

 in the development of 

 the microspores : A and 

 B, X 596; G, x 466.— 

 After Tkeub. 



