INTRODUCTION TO CRYPTOGAMIC BOTASY. 359 



fissure of the jjileus and the gradual obliteration of the upper 

 surface, changes which may be traced with ease in the mesopod 

 Thelephorw, or in the stipitate forms ; the stem may be deve- 

 loped at the expense of the pileus, and if wholly at its expense 

 there will be no development of hymenium at all. In Thele- 

 phora, at least in the more typical species, there are always 

 inequahties in the hymenium ; and it is only the exagge- 

 ration of these which constitutes the genus Oladoderris, which, 

 perhaps, is scarcely tenable. Mere size will not give it any 

 title to distinction, for there are species of Stereum which vie 

 with it in magnitude. One species in Guiana, S. hydrophorum, 

 is remarkable for the time which it holds water. This appears, 

 however, to be only an older form of a species whose cup is at 

 first filled with branched processes, which give it the appearance 

 of a nest. Many of the exotic species of Thelephora and some 

 of our own exhibit a Clavaria-like form in consequence of the 

 hymenium being disposed all round the processes of which it 

 is composed ; but the plan on which this takes place has 

 already been stated. 



391. As in the following tribe, there is a vast variety of 

 colour, insomuch that many of the objects of which it is com- 

 posed are attractive, especially where colour is combined with 

 elegant form and sculpture. One caution is most needful, not 

 only for beginners, but for all half mycologists. As all Hyme- 

 nomycetes arise equally from a mycelium, and that mycelium 

 may be spread out on the matrix, and may assume a stratum 

 of cells, over the threads of which it is composed, before the 

 other parts are formed, it is clear that the earlier stages, and 

 much more the abortive and metamorphosed stages, of many 

 of the higher species, before any hymenium is formed, may 

 simulate Thelephorw. A host of spurious genera and species 

 have thus been admitted into scientific works. No species 

 should, however, be allowed to be autonomous, which has not 

 a perfect hymenium ; and then care must be taken to distin- 

 guish spores and conidia. Gelatinous forms occur in this as 

 in the following group. Some of those usually referred to 

 Corticium belong, however, to Tremella; and Auricularia is 

 scarcely distinguishable from -Exidia. 



