CHAPTER XXIX. 



EU-MYCETES. (b) BASIDIOMYCETES. 



THE Basidiomycetes form the second sub-class of the septate Eu- 

 mycetes. They include most of the large Fungi, such as the 

 Mushrooms, Toad-stools, Shelf-Fungi, and Puff-Balls. These are 

 almost all saprophytes. But the Basidio- 

 mycetes also include the Rusts and Smuts, 

 which are parasitic forms causing disease. 

 Some of these are the most injurious pests 

 to cereal crops, such as the Rust of Wheat, 

 or the Smut of Oats. Some Basidiomycetes 

 also take part in the formation of certain 

 types of Lichens. They are thus very 

 varied in their habit, and include many 

 familiar objects. The characteristic feature 

 is the Basidium, which takes a place in the 

 life-cycle corresponding, to the ascus in 

 the Ascomycetes ; for in both of them 

 there is nuclear reduction, and both pro- 

 duce post-sexual Carpospores. But while 

 in the ascus they are formed internally 

 (Fig. 362, p. 429), in the basidium they 

 are borne externally (Fig. 374). 



FIG. 374. 



Honey Agaric (Armillaria mettea). 

 A , young basidium with two primary 

 nuclei. B, after fusion of the two 

 nuclei. C = a basidium of Hypholoma 

 appendiculatum before the four nuclei 

 derived from the secondary nucleus 

 of the basidium have passed into the 

 four basidiospores. D= passage of a 

 nucleus into the basidiospore. (After 

 Ruhland.) (From Strasburger.) 



In the Basidiomycetes normal sexuality has not been shown to exist, while 

 it is only in the Uredineae or Rusts that organs are found which, though no 

 longer functional as such, are held to be of the nature of sexual organs. This 

 would indicate that the Uredineae are relatively primitive types of the 

 Basidiomycetes. It may be held as probable that all these Fungi were derived 

 from a sexually reproducing ancestry ; but that the sexuality is in abeyance 

 in the more advanced parasites and saprophytes, while vestiges of it remain 

 in the more primitive Rusts. 



441 



