io8 PLANT LIFE. 



curve towards each other, and finally meet; absorption of 

 the walls takes place at the point of contact, and the whole 

 of the protoplasm from one cell passes along the tube formed 

 by the outgrowths from the two cells, and coalesces with the 

 stationary protoplasm of the second cell. To assume the 

 differentiation of sex in the present example, it would be 

 necessary to consider some of the cells of a single plant 

 male, and others female. In other cases the zygospore is 

 formed in the connecting tube between the two cells, the 

 protoplasm from both cells moving to this point. Finally 

 parthenospores — resembling ordinary zygospores, and capable 

 of germination, but differing in being formed from the pro- 

 toplasm of one cell only, without any act of conjugation — 

 are sometimes formed. 



In the genus Mesocarpus and its allies conjugation in a 

 scalariform manner takes place, as in Zygnema ; but the 

 whole of the protoplasm does not contract, a small portion 

 being left behind. The two masses of protoplasm meet and 

 form the zygospore in the connecting tube, but not in the 

 central part, being nearer to one cell than the other ; and 

 this may possibly represent the female cell ; but the sexual 

 differentiation is very slight and vague. Lateral conjugation, 

 also the formation of parthenospores, also occur at times. 

 The chlorophyll in Mesocarpus is arranged in the form of 

 thin, flat plates. Asexual reproduction takes place by the 

 formation of resting-spores from the vegetative cells of the 

 plant. 



The most pronounced difference between the Zygnema 

 and Mesocarpus types consists in the behaviour of the 

 zygospore in the latter, which does not germinate directly 

 after a period of rest, as in Zygnema ; but immediately after 

 its formation it divides into several cells, the central one 



