BoT.— Vol. I.] PEIRCE— NATURE OF LICHENS. 21 7 



information regarding the questions which I hoped to 

 answer in that way. 



To isolate the gonidia of R. rettailata without injuring 

 them is a matter of considerable difficulty owing to their 

 position in the compact thallus. The methods described 

 by others do not lend themselves to the species upon which 

 I have worked. Baranetzky (1869) apparently made no 

 attempt to isolate the gonidia from the hyphge directly, con- 

 tenting himself with making thin hand-sections of living 

 lichens {Collenia, etc.), and placing them in moist cham- 

 bers. The result was that the gonidia multiplied and grew 

 more rapidly than the hyphse, coming out upon the upper 

 surface of the sections and accumulating there practically 

 free from hyphas. Such a method as this, though satisfac- 

 tory with filamentous gonidia in lichens of comparatively 

 loose texture, is ill suited to lichens of close texture, 

 containing spherical gonidial cells {Cystococcus, etc.) The 

 gonidia do not become free under these conditions. The 

 reason for this may lie in the absence of intracellular 

 haustoria in Baranetzk^^'s lichens and in the close invest- 

 ment and the penetration of the gonidial cells by the hyphse 

 of the lichens which I have studied. The gonidia of the 

 latter seem to be too completely in the power of the hyphae 

 to be liberated in this way. 



Teasing out thin sections in water by needles is a slow, 

 tiresome and unprofitable task, for even in this way it is 

 almost impossible to break up the small groups of gonidia 

 closely invested and penetrated by hyphge. These little 

 masses placed in cultures behave like lichens, growing 

 almost imperceptibly; the gonidia do not grow and multiply 

 rapidly and so disrupt the little groups and escape to the 

 surface. 



When air-dry, R. reticulata is tough and leathery, difficult 

 to section, readily bent, but not at all friable. Sections of 

 the air-dry thallus cannot be pulled to pieces dry by needles, 

 and, when placed in a drop of water on the slide, expand 

 without at all loosening the hold of the hyphae upon the 

 gonidia. Teasing out sections cut dry and then placed in 



