22 DOUGLAS HOUGHTON CAMPBELL ON THE 



the walls of the parietal cells to diminish their cavities very considerably (PI. 4, fig. 24) . 

 These cells at the same time absorb much vy^ater, and if a ripe antheridium is placed in 

 water, the tension resulting from the combined pressure of the cells within, and the tur- 

 gidity of the parietal cells from the absorption of water, are sufficient to cause a rupture 

 in the wall of the antheridium. This usually takes place between the two upper cells, 

 the cap-cell being torn in the operation, but sometimes by a rent in the cap-cell only. As 

 this occurs the lower parietal cells become much swollen and press inwards upon the mass 

 of sperm-cells which are thus forced out through the opening. Their discharge is ac- 

 companied by a small amount of mucilaginous matter, evidently the remains of the dis- 

 integrated Avails of the mother-cells. After lying quiescent for a few moments (PI. 4, 

 fig. 27) the vesicle in which the antherozoid is contained bursts and the antherozoid swims 

 rapidly away with a twisting movement due to its spiral form. It consists of hyaline pro- 

 toplasm, somewhat flattened and enlarged at the forward end, which sometimes shows 

 two or three indistinct and close coils, the hinder part being composed of one or two 

 open and complete turns of the spiral (PL 4, fig. 28). The cilia are numerous, being 

 developed principally on the antei-ior coils but also extending back to the beginning of 

 the larger ones. They are directed somcAvhat backward, as is plainly seen in treating 

 the antherozoid with iodine, Avhich causes it to become deeply stained and somewhat con- 

 tracted and the cilia rigid and sharply defined. The end tapers to a point Avhich some- 

 times is much prolonged. AVhen the antherozoid has recently escaped, the movement of 

 the cilia is so rapid as to render them almost invisible, but as it dies the movement be- 

 comes slower and is then seen to be iindulatoiy, the movement seeming to begin at the 

 point nearest the body and to pi'oceed outward toward the tip of the cilium. This move- 

 ment continues for some time after it ceases to be strong enough to propel the anthero- 

 zoid. 



It sometimes happens that the antherozoid does not become entirely free from the 

 membrane of the cell in which it lies so that its movements are much hampered, the vi- 

 brations of the cilia being only sufiicient to cause a rotation of the cell. It may subse- 

 quently free itself entirely or it may never escape completely. As the antherozoid swims 

 away, there is seen attached to it a delicate vesicle which absorbs Avater and becomes 

 much distended. Contained in this are several line granules, the Avhole being the re- 

 mains of the mother-cell of the antherozoid. This vesicle is sometimes attached to the 

 pointed end of the antherozoid, sometimes it adheres for a considerable part of its length. 

 It occasionally happens that the antherozoids are imperfect in form, the hyaline pro- 

 toplasm that constitutes the body not being sharply differentiated from the gi-anular pro- 

 toplasm of the central parts of the mother-cell. In such eases the anthei'ozoid is club- 

 shaj^ed with the cilia at the pointed end, and the movement is less decidedly rotary. 



The archegonia, like the antheridia and root-hairs, arise from the superficial cells of 

 the prothallium and are, therefore, morphologically trichomes. Unlike the antheridia 

 they are confined to a special part of the prothallium, being formed only on the lower 

 sui'face of the cushion of tissue Avhich lies at the bottom of the cleft in the front of the 

 prothallium. If the earlier archegonia are not fertilized, ucav ones continue to form as 

 long as the prothallium grows, the latter in such cases reaching a considerable size and 

 bearing, sometimes, a hundred or more archegonia. In such cases, the cushion of tissue, 



