410 COMPARATIVE MORPHOLOGY OF FUNGI 



does not seem obvious because in them the fructifications may grow 

 actively during and after their formation. In the higher forms, as in the 

 Agaricales and Gasteromycetes, the fructifications are formed from the 

 interior of hyphal tangles; consequently, active growth ceases as soon as 

 differentiation of these hyphal masses is ended. Since their size chiefly 

 depends on the dimensions of their original fundaments, they develop 

 further only by expansion (elongation) and similar processes. There- 

 fore, these fructifications are mature when differentiation ceases. No 

 longer, as the resupinate crusts, are they a complex of relatively inde- 

 pendent elements of unequal age (e.g., the older in the middle and the 

 younger at the edge), but an organic entity which is young as a whole and 

 matures as a whole. 



Parallel with this gradual limitation of the dimensions of the fructifi- 

 cations, and with their development out of tuberiform hyphal tangles, 

 hymenia are formed in the interior of the fructification. In this, one 

 may distinguish three stages which merge into each other. The first, or 

 gymnocarpous, stage includes all crust and bracket forms and some 

 pileate forms of simple structure, where the basidial layer is formed on 

 the free surface of the fructification (Fig. 286). In the second, or 

 hemiangiocarpous, stage, which includes the majority of the pileate 

 forms and in which the fructifications develop directly from the tuberiform 

 fundaments, the sporiferous layer is differentiated from the tissue in the 

 interior of the fundaments. Before the completion of their development, 

 they are freed from the universal veil and pass through the last stages of 

 their development as in the gymnocarp type (Fig. 293); their ontogeny 

 is the reverse of their supposed phylogeny. Finally, the third and 

 highest, or angiocarpous, stage includes the Gasteromycetes, where the 

 sporiferous layer remains enclosed in the universal veil (Fig. 319 to 321) 

 until the basidia mature. 



The structure of the hymenia is apparently correlated with the tran- 

 sition from growth unlimited by time and space, to morphological com- 

 pactness at maturity and, from the gymnocarpous to angiocarpous origin 

 of the hymenia. In the resupinate forms, in which the hymenia can 

 spread out laterally in an unlimited manner by the successive addition of 

 new elements, the surface is smooth and level. These smooth hymenia 

 occur also in some of the higher families which are directly connected to 

 these resupinate crusts; all sorts of indentations, elevations, folds, teeth, 

 spines, tubes, etc., help to increase the area of the hymenium (Fig. 290). 

 In the higher forms, these structures increase and result in the lamellae, 

 alveoles, tubes, etc., of the mushrooms. 



In the selection of these forms, the production of the greatest possible 

 number of spores with the smallest possible use of material will not have 

 been of prime importance; for the senescent fructifications (e.g., the 

 edible mushrooms) still possess lavish amounts of food material which 



