CHAPTER XXVII, 



BASIDIOMYCETES. 



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

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

 rooms, Toad-stools, Shelf-Fungi, and Puff-Bails. These are almost all 

 saprophytes. But the Basidiomycetes 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 produce 

 post-sexual spores equivalent to Tetra- 

 spores. But while in the ascus they are 

 formed internally (Fig. 316, p. 417), in the the basidium have pass 



J \ t> ° ' r t x //j ""* four basidiospores. Z)=passage of a 



basidium they are borne externally, as RuhS^ 

 Basidiospores (Fig. 328). 



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

 it is only in the Uredinales or Rusts that organs are found which, though not 

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

 would indicate that the Uredinales are relatively primitive types of the 

 Basidiomycetes. It may be held as probable that all these Fum;i were derived 

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

 in the more advanced parasites and saprophytes, while evidence of it remains 

 in the more primitive Rusts. 



b.b. 431 2E 



Fig. 328. 



Honey Agaric (Armillaria mellea). 

 A, young basidium with two primary 

 nuclei. B, after fusion of the two 

 nuclei. C =a basidium of Hypholoma 

 appcndiculatum before the four nuclei 

 derived from the secondary nucleus 



