GAMETOGENESIS AND SPOROGENESIS 



203 



fragments which together form the ciha-bearing rod, as in certain vascular 

 plants (Sharp, 19206). In the spermatozoids of i^zccardza (Fig. 116, i^), 

 Pellia, and certain other genera the two cilia spring from different points,^ 

 at which basal granules may be seen. 



Recent studies on spermatogenesis in mosses have revealed a remark- 

 able parallelism between the behavior of cell elements here and that in 

 animal spermatogenesis. In the multiplying spermatogenous cells 

 ("androgones") of Polytrichum the plastids form one or two masses, 



Fig. 121. — Diagram of spermatogenesis in Polytrichum. In 1 the apical body {A) is 

 separating from the limosphere remnant (L). B, blepharoplast. C, cilia. A'^, nucleus. 

 {After Weier, 19316.) 



which appear after certain fixations like clumps of granules and as large 

 plates, or, after other procedures, like a series of chromophilic plates in a 

 chromophobic substance (see p. 80). In each cell generation these 

 bodies undergo division (Fig. 120). In each cell of the last generation 

 but one, a centrosome with radiations in the cytoplasm divides into two. 

 These move apart and occupy the spindle poles during the last mitosis, 

 which differentiates the spermatids ("androcytes"). 



In the androcyte the plastid becomes a body known as the limosphere. 

 It becomes somewhat oblong and buds off a small differentiated portion 

 from one end; this is the apical hody^ (Fig. 121). Meanwhile the centro- 



' Steil (1923), Showalter (1926a), Mlihldorf (1931). 



* The limosphere was named by M. Wilson (1911). Allen (1917a) gave the first 

 adequate description of it, discovered its division to form the apical body, and pointed 

 out evident references to it in the earlier literature. Its derivation from plastids was 

 demonstrated by Weier (1930, 19316, 1932), see page 81. The granules and plates 

 in the earlier spermatogenous cells were called "kinetosomes" and "kinoplasmic 

 plates" by Allen (1912). Sapehin's (1915) claim that they are plastids was confirmed 

 by Bowen (19276) and Weier. 



