168 



BOTANT. 



mersed in cavities which show only as bfackish lines or 

 dots on the surface of the lichen-hody. 



3S2. The spores germinate by sending out one or more 

 tubes which develop directly into the ordinary filaments of 

 the lichen-body. Experiments have shown that these fila- 

 ments will not grow for any great length of time unless 

 they can come into contact with a protophyte of the proper 

 species to which they can become attached. The lichen- 

 filaments then grow rapidly and surround the protophytes, 

 and in the moist tissues thus formed the latter find protec- 

 tion and ample opportunity for growing. There is thus an 



Fio. 93.— Sections of gelatinous Lichens (CoUema), showing (in A) a carpogone, 

 c, with its projection, a, and (in B) a cavity (spermogone) emitting sperm-cells 

 (spermatia). The gonidia here (6, 6) are species of NoBtoc. Highly magnified. 



association between these plants which is mutually bene- 

 ficial. The lichen lives parasitically upon the protophytes, 

 to which it in return furnishes shelter and moisture. 



353. We know very little as to the sexual organs of 

 lichens. A few years ago Stahl discovered them in CoUe- 

 ma, a low form of gelatinous lichens. The carpogone is a 

 tightly coiled spiral filament, which sends up a prolonga- 

 tion to the surface (Fig. 93, A, c, d). Fertilization takes 



