358 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



developed, than a distinct type. A vast quantity, however, of 

 the fungoid growths which appear on fallen timber and 

 branches, exhibit mere differences of colour and substance, with- 

 out any of hymenium, except that in some species there are little 

 bristles, and in others peculiar processes, calling to mind those 

 which exist on the hymenium of the higher Fungi, and which 

 may ultimately j)rove sexual. They may be dry, waxy, byssoid 

 or moist, tender or gelatinous, without much difference as 

 to hymenium, and it is on this account that the species are 

 so difficult to distinguish. The hymenium is essentially 

 inferior, avoiding the light ; and hence in many species, even 

 those which are resupinate, when accidentally superior, it 

 becomes inferior by the detachment of the pileus from the 

 matrix. This occasionally takes place in most species to a 

 greater or less extent ; but in some it is normal ; and a step 

 further leads us to stemless but expanded dimidiate or flabel- 

 late forms. Precisely the same series of phenomena holds in 

 all the other groups, a circumstance which shows that a form 

 is not necessarily distinct because it is resupinate. Indeed, 

 resupinate species are always to be regarded with caution, and 

 resupinate forms even of nobler species may occur. 



389. One genus essentially tropical, Dictyonema, is worthy 

 of notice, because it has been considered an Alga. Like Cora, 

 it grows in exposed damp places, on moss or other vegetables ; 

 and as it does not always perfect its hymenium, and is very 

 generally felted with a species of Calothrix, no great blame can 

 be attached to those who have misunderstood its affinities. 

 Both in Cora and Dictyonema the hymenium cracks up into 

 fragments, so as to exhibit the appearance of little parasitic 

 Pezizce. The substance of the pileus, in fact, grows so fast that 

 the hymenium cannot keep pace with it, and so is broken up. 

 Cora was originally referred to the genus Ulva, but with very 

 little reason, even on principles which were generally received 

 at the time of its first discovery. 



390. But besides these there are forms essentially mesopod 

 or lateral ; yet even here, again, the mesopod may become late- 

 ral by only a partial development of the pileus. Both the 

 lateral and mesopod forms, again, may become clavarioid by the 



