106 BOTANY. 



Shortly before the archegonium opens, the canal cells become disorgan- 

 ized in the same way as in the bryophytes, and the protoplasm of the 

 central cell contracts to form the egg cell which shows a large, central 

 nucleus, and hi favorable cases, a clear space at the top called the "recep- 

 tive spot," as it is here that the spermatozoid enters. When ripe, if placed 

 in water, the neck cells become very much distended and finally open 

 widely at the top, the upper ones not infrequently being detached, and 

 the remains of the neck cells are forced out (Fig. 66, /). 



The antheridia (Fig. 66, J, M) arise as simple hemispherical cells, in 

 which two walls are formed (K i, n), the lower funnel-shaped, the upper 

 hemispherical and meeting the lower one so as to enclose a central cell 

 (shaded in the figure), from which the sperm cells arise. Finally, a ring- 

 shaped wall (L in) is formed, cutting off a sort of cap cell, so that the 

 antheridium at this stage consists of a central cell, surrounded by three 

 other cells, the two lower ring-shaped, the upper disc-shaped. The central 

 cell, which contains dense, glistening protoplasm, is destitute of chloro- 

 phyll, but the outer cells have a few small chloroplasts. The former 

 divides repeatedly, until a mass of about thirty-two sperm cells is formed, 

 each giving rise to a large spirally- coiled spermatozoid. When ripe, the 

 mass of sperm cells crowds so upon the outer cells as to render them 

 almost invisible, and as they ripen they separate by a partial dissolving 

 of the division walls. When brought into water, the outer cells of the 

 antheridium swell strongly, and the matter derived from the dissolved 

 walls of the sperm cells also absorbs water, so that finally the pressure 

 becomes so great that the wall of the antheridium breaks, and the sperm 

 cells are forced out by the swelling up of the wall cells (N, 0). After 

 lying a few moments in the water, the wall of each sperm cell becomes 

 completely dissolved, and the spermatozoids are released, and swim 

 rapidly away with a twisting movement. They may be killed with a little 

 iodine, when each is seen to be a somewhat flattened band, coiled several 

 times. At the forward end, the coils are smaller, and there are numerous 

 very long and delicate cilia. At the hinder end may generally be seen a 

 delicate sac (P, -y), containing a few small granules, some of which usually 

 show the reaction of starch, turning blue when iodine is applied. 



In studying the development of the antheridia, it is only necessary to 

 mount the plants in water and examine them directly ; but the study of 

 the archegonia requires careful longitudinal sections of the prothallium. 

 To make these, the prothallium should be placed between small pieces of 

 pith, and the razor must be very sharp. It may be necessary to use a little 

 potash to make the sections transparent enough to see the structure, but 



