92 



MANUAL OF BOTANY 



paraphyses, and those which give rise to the spores, the basidia. 

 Each basicliimi puts out four dehcate Gulgrowthp, closely 

 resembling those of the promycehnm of the Uredinese, and 

 from each of these a single gonidium or spore is abstricted. 



These, from their mode of 

 Fig. 854. origin, are known as hasi- 



diospores or hasidiogonidia 

 (Jig. 854, c, g). 



The form of the fructifi- 

 cation varies a good deal in 

 different groups. In some 

 the hymenium is exposed 

 from its first formation ; in 

 others it is covered for a 

 time by the velum partiale ; 

 in yet others it is always 

 surrounded by a membrane, 

 which is then known as the 

 peridium, as in the Gastero- 

 mycetes, or the velum uni- 

 versale^ as in some Aga- 

 ricinae. The hymenium is 

 also variously arranged ; in 

 the true mushrooms it 

 covers the gills as described ; 

 in the family Polyporeye it 

 lines pits or tubes on the 

 under surface of a flattened 

 expansion ; in the Gastero- 

 mycetes it is formed in the 

 interior of the fructification 

 in a number of chambers. 



The basidia are usually 

 unicellular, but m one 

 group, the Protobasidiomy- 

 cetes, they are divided by 

 septa, sometimes trans- 

 verse, sometimes longitu- 

 dinal, forming fom' cells, each of which produces a single goni- 

 dium. These forms approach the promycelium of the Uredinese 

 very closely. 



Vegetative reproduction occurs in this group, by the forma- 

 tion of gemmae, which commonly arise on the vegetative 



Fig. 854. a. Section of five gills of the Mush- 

 room. B. One gill more highly magnified. 

 /. Trama. e. Hymenial layer, c. Hymenial 

 and sub-hymenial layers, h. Basidia. g. 

 Basidiospores. i. Paraphyses. ;'. Sub-hy- 

 menial layer. After Sachs. 



