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 Lyco podium. 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- 
prowth which is cut off bv a, 
FIGS. 345-349. Anthendiumof Eqmselum: 
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, . . ... ,.. . T 
showing the papillate protruding cell (peri- the antheridium (fig. 34 6). In 
clinal wall below), in which are shown two this cell an apical Cell with 
segments (the third behind) cut off by the tnree cu tting faces is formed, 
apical cell, the dome or cap cell, and the en- 
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 w hi c h produces the spermatoge- 
BELATEFF. . 
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 
