CABPOSPOREJE. 



141 



compacted into a pseudo-pareucliyma, and in tlie medul- 

 lary portion distinct. Scattered through the interior, or 

 disposed in one or more distinct layers, are numerous 

 green, bluish-green, or brownish-green cells, called gonidia. 

 These cells may be isolated, or in groups ; or they 

 may be rows, or chains of cells, and are capable of 

 multiplication by fission. They are connected with the 

 hyphse by one or more branches from the latter, or they 

 may be united directly to an intermediate or terminal cell 

 of the hyphae. The latter were, for a long time, supposed 

 to produce them. Now it 

 is held that the gonidia 

 are simply imprisoned 

 AlgBB, which assimilate 

 the food to be appropri- 

 ated by the Lichens — a -^^^^^^g^ --"'^^^-^^.Siasv^iito 

 peculiar kind of parasit- 255 256 



ism which seems to be mutually advantageous to the two 

 plants. The reproduction is similar to the other Asco- 

 mycetes (Fig. 256). The asci are either collected in a 

 disk-like surface (gymnocarpous lichens), or enclosed in 

 cavities or perithecia (angiocarpous lichens) ; and in either 

 case called an apoihenum. Of the numerous Lichens, a 

 few furnish important commercial products; thus, from 

 Roccella tindoria, the dye orchil and " litmus" are obtained ; 

 and food is furnished by the Iceland Moss ( Ceiraria island- 

 icd), and others. The Reindeer Moss {Cladonia rangi- 

 ferina) furnishes food to the reindeer. 



4. Uredineae. The plants are parasitic in habit, and 

 polymorphic ; that is, in their life-course they take on at 



-»-i:^ ■ "^.^i^Si; ^"'- otic :^&=^ r.7 



Fig. 255. Cladonia, a Lichen ; «/, the fruit, or apothecium. Fig. 256. Asci from 

 the same, highly magnified. 



