5 



BASIDIOMYCETES. 



Naked spores borne on basidia are, as already stated, the 

 morphological features that are supposed to be indicative of 

 relationship amongst thousands of fuugi, which in every 

 other particular are frequently very dissimilar. A typical 

 basidium is the club-shaped terminal cell of an ordinary 

 hypha that becomes densely filled with protoplasm. From 

 the rounded apex of the basidium four very slender spine- 

 like processes — the steru/mata — are produced ; the tip of each 

 sterigma becomes swollen, the swollen portion becoming 

 differentiated into a spore. 



In primitive types of Basidiomycetes the hymenium covers 

 the entire exposed surface of the sporophore, which shows 

 but little differentiation, as in Tremella, Corticium, &c. In 

 the last-named genus and its allies, the sporophore resembles 

 a crust-like expansion closely adnate or attached to the 

 'natrix throughout its entire surface, when it is said to be 

 resujjinate, the upper or free surface being entirely covered 

 by the hymenium. The next phase of evolution towards the 

 highest form is where a greater or less portion of the crust- 

 like sporophore is free fiom the matrix and rejtexed or curved 

 downwards ; this condition of things is seen in many species 

 of Stereum. A third type, the dimidiate stage, is illustrated 

 by many species of Poli/jiorus that are attached by a broad 

 edge to the matiix, the fungus standing out at right angles 

 to the matrix, and often of a more or le.-^s semicircular form, 

 the upper barren surface being the pileus, the under fertile 

 surface the hynienium. 



Following on, we come to species with a lateral stem, due to 

 the broad base of attachment of the dimidiate type l>eing 

 narrowed to stem-like dimensions. Finally we come tc) 

 mesoj)od or central-stemmed species, as seen in the mush- 

 room. 



In all the higher forms, Ihe hymenium is continuously 

 spread over both surfaces of thin plates t)f tissue, which are 

 variously arranged in different grou2)s, and furnish important 



