6 . FUNGUS-FLORA. 



characters ; these plates take the form of gills or lamellae in 

 Agaricus, &c., pores in Polyporus, Boletus, &c., or are variously 

 contorted and form a cavernous structure in Lycoperdon, 

 Rhizopogon, &c. 



No trace of sexual organs is known to exist in any 

 member of the group. 



The Basidiomycetes are divided into two primary groups, 

 briefly characterised as follows : 



HYMENOMYCETES. 



Hymenium exposed from the first, or in all cases before 

 the spores are mature. 



GASTROMYCETES. 



Hymenium enclosed within a continuous membrane or 

 peridium until the spores are mature. 



GASTEOMYCETES. 



Opinion differs as to the origin or starting-point of the 

 peculiar features that give individuality to the present 

 group. The late Professor De Bary saw in some points of 

 resemblance with certain species of Polyporus the probable 

 starting-point of the group under consideration.* The 

 Hymenogastreae, including the comparatively simple sub- 

 terranean species, are universally considered as the starting- 

 point from which all the other families of the Gastromycetes 

 have been derived, and I have indicated the very close 

 agreement in many important points of structure, habitat, 

 &c., I between the Hymenogastreae and the Tuberaceae, an 

 ascigerous family of subterranean fungi including the truffle, 

 and consider that the Gastromycetes have evolved from the 

 Tuberaceae through the Hymenogastreae, due to the gradual 

 conversion of asci into basidia. 



In the simplest subterranean forms there is a continuous 

 external compact wall or peridium, which remains perfectly 

 closed until the spores are mature, and even then shows no 



* ' Fungi Mycetozoa and Bacteria.' Eng. Ed. 



t ' A Monograph of the British Gastromycetes,' 'Annals of Botany,' 

 vol. iv. 1889. 



