08 



PLANT STRUCTURES 



nected together, so that a mycelium bearing uredospores is 

 called a Ureclo^ one bearing teleutospores a Puccinia^ and 

 one bearing »cidia an j^cidium ; but what forms of Uredo^ 

 Pucci)iia^ and ^Fcidium belong together in tlie same life 

 cycle is very difficult to discover. 



Another life cycle which has been discovered is in con- 

 nection with the " cedar apples " which appear on red 

 cedar (Fig. 54). In the spring these diseased growths be- 

 come conspicuous, especially after a rain, when the jelly- 

 like masses containing the orange-colored spores swell. 

 This corresponds to the phase which produces rust in 

 wheat. On the leaves of apple trees, wild crab, hawthorn, 

 etc., the aecidium stage of the same parasite develops. 



4. Basidiomycetes {Basidium- Fungi). 

 48. General characters. — This group includes the mush- 

 rooms, toadstools, and puffballs. They are not destructive 



parasites, as are many 

 forms in the preceding 

 groups, but mostly harm- 

 less and often useful sap- 

 rophytes. They must 

 also be regarded as the 

 most highly organized of 

 the Fungi. The popular 

 distinction between toad- 

 stools and mushrooms is 

 not borne out by botan- 

 ical characters, toadstool 

 and mushroom being the 

 same thing botanically, 

 and forming one group, 

 puffballs forming an- 

 other. 



As in ^cidiomycetes, 



Fig. 55. The common edible mushroom, 

 Agaricus campestris.— After Gibson. an obsCUrC SCXUal prOCCSS 



