POLYSIPHONIA. 45 



segmentation of the young cystocarp, and the formation of the 

 trichogyne as an elongated thread-like cell, which overtops the 

 apex of the branch on which it is borne ; its fertilisation by a 

 spermatium, and the further growth of the cystocarp. 



As examples of simpler structure of the fruit may be suggested 

 Batrachospermum, and Polyides or Dudresnaya, the latter genera 

 being specially remarkable for the indirect character of the process 

 of fertilisation. 



The case of Lemanea is worthy of note : the carpogonia are 

 formed internally, but with a projecting trichogyne. In summer 

 the carpospores are to be found borne on branching filaments 

 which occupy the large mucilage cavities in the thallus. 



In the forms with more complicated structure, the cystocarp is 

 often embedded in the tissue of the thallus : sections should be 

 cut to illustrate this in Chondrus crispus. 



X. Embed mature cystocarps of P. fastigiata in 

 paraffin, and cut from them median longitudinal sections: 

 mount in glycerine, and observe 



1. The short thick stalk of the cystocarp. 



2. Its wall, consisting of small, closely aggregated 

 cells, and with an opening or ostiole at the apex. 



3. The central cavity, surrounded by the wall, and 

 filled more or less completely, according to age, with 

 elongated, club-shaped cells, having dark protoplasm, 

 and swollen walls : these are the carpospores. 



The following points are further to be observed in 

 longitudinal sections, viz. 



1. The formation of the carpospores by budding from 

 the base of the cavity of the cystocarp. 



2. The contents of the spores in various stages of 

 escape from their cell-walls, and of passage through 

 the ostiole, so as to escape freely, as rounded and naked 

 protoplasmic bodies, out from the cystocarp. 



The artificial germination of the spores is a 



