242 PLANT LIFE. 



by closely-packed upright cells of two kinds. Some 

 are very narrow, though a little swollen at the tip 

 {pctraphyses) ; the others {asci) less numerous, are oval, 

 and each contains eight brown-walled spores {ascospores). 

 The surface of the cup is generally covered by a dusty 

 material in which algal cells also occur, so that the 

 insects carry off, not only the fungus spores, but also 

 algal cells. This lichen cup is probably the result of a 

 process of sexual fertilisation. It may be taken as 

 corresponding to the " cystocarp " of the Red Algae or 

 Florideae. In these a chain of cells, of which one is 

 the ^^^ cell, terminates in a long hair-like cell called 

 the trichogyne. The male cells are produced in clusters 

 situated like the trichogynes on the ends of the branches. 

 These male cells are carried to the trichogyne. One of 

 these male cells then enters the trichogyne, and passes 

 down inside it until it reaches and fuses with the Qgg 

 cell. After this sexual union, a great development takes 

 place, not only in the Qgg cell, but in those cells which 

 surround it. Eventually by the growth and division of 

 the Qgg cell and its neighbours the cystocarp is formed. 

 In the lichens the process seems to be very similar, and 

 trichogynes are also formed, but the result is the lichen 

 cup. Only the asci are formed from the ^gg cell itself, 

 the others {pai-aphyses, and those forming the border of 

 the cup) are produced by the neighbouring cells.^ 



Lichens also reproduce by a sort of budding. Small 

 pieces of the substance break off, and are carried away 

 by the wind. These are called soredia, and generally 

 look like greyish-green dust. The lichens have also 

 non-sexual spores, which are produced in small pits or 



•^ Further details may be found in Dr. Darbishire's account. It is 

 curious to find the fungus of the lichen showing a great similarity in its 

 reproduction to the Ked Algae. The Alga of the lichen belongs to a 

 totally different group. 



