148 



MORPHOLOGY 



at least it secures the development of male and female gametophytes 

 in close proximity. 



Gametophyte. The gametophyte is a small, green, branching rib- 

 bon, being strictly a thallus, without any of the subterranean develop- 

 ment that characterizes Lycopodinm. Although the gametophytes are 

 usually dioecious, and the female gametophytes are larger and more 

 massive than the male (figs. 343, 344), the spores are all approximately 

 the same size. Certain of the ancient representatives of the Equise- 

 tales, however, have been found to be heterosporous. 



Antheridium. The antheridium is interesting in that it shows two 

 kinds of development, dependent upon its position. If it occurs in the 



axial region of the thallus, it 

 develops as usual among euspo- 

 rangiates; that is, a superficial 

 initial cell is divided by a peri- 

 clinal wall, the outer cell pro- 

 ducing the wall of the anther- 

 idium, the inner cell producing 

 the spermatogenous tissue (figs. 

 345, 347, 348). If it develops 

 in a terminal position on the 

 thallus, the superficial initial 

 cell forms first a papillate out- 



FIGS. 345-349 Antheridium of Equisetum: g rowth > which is CUt , ff b ? a 



345, one type of development, showing the peri- periclinal wall, and it is this 



clinal^ division, the inner cell being spermatog- protruding cell that develops 



enous*; 346, the other type of development, . . .,. ff . , N T 



showing the papillate protruding cell (peri- the antheridium (fig. 346). In 



clinal wall below), in which are shown two this Cell an -apical Cell with 



segments (the third behind) cut off by the three cut ting faces is formed, 



apical cell, the dome or cap cell, and the en- - , . , 1M n 



closed spermatogenous cell; 3 47, 348, nearly and then a domelike cap Cell 



mature antheridia of the first type; 349, a is Cut off, leaving" a central cell, 



sperm. 345-348, after GOEBEL; 349, after which produces the spermatoge- 



BELAJEFF. T - i u r 



nous tissue, invested by four 



peripheral cells, which develop the wall of the antheridium. This 

 type of antheridium development is characteristic of certain modern 

 ferns. The sperms are very large, spirally coiled, and multiciliate 



(fig- 349)- 



Archegonium. The archegonium always develops from the massive 

 axial region and in the axil of a branch. It develops as among other 



348 



349 



