174 BOTANY 



CLASS II. BASIDIOMYCETES 



The second great division of the Eumycetes, the Basidiomycetes, 

 comprises a large number of the most conspicuous and highly 

 developed Fungi, such as the Mushrooms and Toadstools, Puffballs, 

 Kusts, Smuts, etc. They always possess a well-developed mycelium, 

 which may be composed of quite distinct elements, or these may be 

 closely compacted into rootlike masses, or leathery plates, which 

 grow to great size. The latter type is found in some Fungi which 

 grow upon decaying wood and form, the tough leathery mycelium 

 between the woody layers. 



Reproduction. Various forms of spores are produced, but the 

 characteristic type is the basidiospore. The basidiospores are single 

 conidia borne* upon special structures, basidia, which are usually 

 undivided club-shaped cells, upon whose end the spores are pro- 

 duced, attached to delicate prominences, the sterigmata (Fig. 147, F). 

 The basidiospore appears first as a small swelling at the apex of the 

 sterigma, into which passes part of the protoplasm from the basidium. 

 The spore usually develops a thickened wall, but in the lower forms 

 like the Rusts and Smuts the wall of the basidiospore remains very 

 delicate, and the spores germinate as soon as they are ripe. In the 

 lower types (Hemibasidii) the basidia are divided by septa, and are 

 less constant in form than those of the higher types (Eubasidii), 

 which are also in most instances arranged in a definite hymenium 

 covering certain portions only of the conspicuous spore-fruit. This 

 arrangement is not nearly so evident in the lower members of the 

 class. The latter are largely parasites upon Flowering Plants, while 

 the Eubasidii are, for the most part, saprophytes. 



The Basidiomycetes may be arranged in two series, the Hemiba- 

 sidiese, a small group of parasitic forms in which the basidia arise 

 directly from certain resting-spores ; and the Eubasidiese, in which 

 true basidia are found which do not, as a rule, arise directly from 

 resting-spores. Of the Hemibasidieae the greater part are the so- 

 called Smuts (Ustilagineae), very destructive parasites upon many of 

 the higher plants. 



SUBCLASS I. HEMIBASIDIEAE 



The Ustilaginese derive their popular name from the masses of 

 sooty-black chlamydospores which they produce. The most familiar 

 of these to American students is the common Corn-smut (Ustilago 

 maydis), which so commonly attacks the flowers and young ears of 

 Indian-corn. The sprouting corn is infected soon after it appears 

 above ground, and the parasite grows within its tissues much as does 

 the White-rust within the tissues of its host. While the mycelium 

 grows for the most part in the intercellular spaces, it sends suckers 

 into the host-cells, and the hyphae may themselves penetrate into the 

 cells. The hyphse are septate, thick-walled, and irregular in outline. 



