CEYPTOGAMOUS OR FLOWERLESS PLANTS. 337 



quence of fertilization, develops into a sort of pod, the Sporangium 

 or Spore-case, filled with a multitude of spores which receive no in- 

 dividual fecundation ; this organ, from its general analogy to the 

 pistil, has been termed a PistiUidium. The antheridia of Mosses 

 and the like occur either in the axils of the leaves, or collected 

 into a head at the summit of the stem. They are found either 

 in the same heads as the pistiUidia, or in distinct heads on the 

 same individuals (monoecious), or on separate individuals (dioe- 

 cious). The antheridium (Fig. 1307) is merely a cylindrical 

 or club-shaped sac, composed of a single layer of cells, united 

 to foi-m a deUcate membrane ; within which are developed vast 

 numbers of minute, very delicate cells, completely filling the sac. 

 The sac bursting at its apex when mature, the delicate vesicles 

 are discharged. Each of these contains a slender filament, thick- 

 ened at one end and tapering off to a fine point at the other : it may 

 be seen through the transparent walls, spirally coiled up in the interior 

 of each vesicle. When these vesicles are extruded in water under 

 the microscope, the contained filaments may be seen to execute Uvely 

 movements, wheeling round and round in the vesicle, or, when dis- 

 engaged from the latter, and assuming a corkscrew form, at the same 

 time advancing forward, the thin end of the filament almost always 

 preceding. Minute observation, which is very difficult, both from 

 the rapidity of the motion (which, however, is arrested by poisons) 

 and from the great delicacy of the whole structure, shows that the 

 movements arise from two long and extremely delicate cilia, attached 

 to the tapering end of the filament. These are the spermatozoids, 

 or true fei-tilizing organs. The pistiUidia (Fig. 1306), which ap- 

 pear at the same time as the antheridia, and often mixed with them, 

 are flask-shaped bodies (like an ovary in shape), with a long neck 

 (resembling a style), composed of a cellular membrane. The neck 

 is perforated by an open canal, leading to a cavity below, at the base 

 of which a single cell is the germ of the future sporangium or spore- 

 case. Upon this the spermatozoids, or spiral filaments of the an- 

 theridia, act, one or more of them reaching it by finding their way 

 down the canal of the pistiUidium. Then this cell commences a 

 special development, divides into two, and proceeds by ordinary cell- 

 multiplication to build up the sporangium or capsule, in which a 

 countless number of minute spores are produced. The spores of 

 Mosses are formed in the same way as pollen-grains, which they 

 much resemble in structure, being single cells with a double coat, of 

 29 



