314 PART III. THE CLASSIFICATION OF PLANTS. 



or more compound gonidiophores. The most remarkable solerotia 

 are those of Agaricus melleus, a Fungus which is very destructive 

 to timber. The mycelium gives rise to dark-coloured compact 

 strands of hyphae, of the pseudo-parenchymatous structure char- 

 acteristic of sclerotia ; but they are peculiar in possessing con- 

 tinued apical growth, and by this means they soon become long 

 filaments, known as Rhizomorpha. It is in this way that the 

 Fungus spreads from tree to tree : the Rhizomorpha-fi laments 

 grow underground from the roots of an infected tree to those of 

 a healthy tree (usually a Conifer) ; it penetrates into them and 

 spreads in the tissues external to the wood in the form of a 

 white fan-shaped mycelium. The compound gonidiophores (Agar- 

 icus melleus) are borne either on the subterranean Rhizomorpha- 

 filaments, or on the parasitic mycelium ; in either case the goni- 

 diophores come to the surface. 



The homologies of the reproductive organs of the Basidiomy- 

 cetes are not difficult to trace. The development of the basidio- 

 gonidia on the basidia, more especially in the Protobasidiomycetes, 

 recalls the germination of the teleutogonidia and resting-gonidia 

 of the Uredineas and Ustilagineae respectively ; of those Uredineae 

 in particular (Leptouromyces, Leptopuccinia) in which the teleu- 

 togonidia germinate without having fallen off the plant bearing 

 them (compare Fig. 217 with Fig. 220), the sterigmata being all 

 that remains of the promycelium. A mushroom is, then, a com- 

 pound gonidiophore producing basidia (or teleutogonidia) which 

 germinate, without falling off, and give rise to basidiogonidia 

 (or sporidia). The gonidia developed on the simple gonidiophores 

 (when present) of the Basidiomycetes may be compared with the 

 similar gonidia of the Ustilagineee, and with the uredogonidia of 

 the Uredineae. These homologies may be comprehensively indi- 

 cated in a tabular form : 



Gametoptiyte. Sporophyte. 



Uredineae. uredogonidium teleutogonidium sporidium tecidium with 



Ustilagineae gonidium resting-gonidium sporidium [spores. 



Basidiomycetes gonidium basidium basidiogonidium 



It will be seen that in neither the Ustilagineae nor the Basidio- 

 mycetes is there any organ to correspond with the oecidium of the 

 Uredineae. 



The foregoing table also indicates the nature of the life-history 

 of the Basidiomycetes. As in the Ustilagineae, so in the Basidio- 



