CABPOSPOB.EM 



141 



compacted into a pseudo-parenchyma, and in the 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 gorddia. 

 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 

 hyphae 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 °2- v ^ V- 

 is held that the gonidia 

 are simply imprisoned 

 Algse, which assimilate 

 the food to be appropri- 

 ated by the Lichens — a 

 peculiar kind of parasit- 



265 



266 



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 apothedmn.- Of the numerous Lichens, a 

 few furnish important commercial products ; thus, from 

 JRoccella tinetoria, the dye orchil and " litmus" are obtained ; 

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

 iea), and others. The Keindeer 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 



Fig. 265. Cladonia, a Lichen ; ap, the fruit, or apothecium. Fig. 256. Asci from 

 the same, highly magnified. 



