342 INTRODUCTION TO CRYl'TOGAMIC BOTANY. 



appendages, or we have a second separating readily from the 

 other, as in Bovista. In these cases there may either be a 

 rudiment of a stem, or the peridium may be perfectly sessile. 

 The stem, m fact, is nothing more than a continuation of the 

 barren cells which underlie the hymenial mass, and either 

 pass into it directly, or are separated by a more or less definite 

 stratum of cells, as in Lycoperdon ccelatum. The hymenial 

 mass, again, may either be simple or compound, divided, that 

 is, as in Polysacoum, into numerous secondary peridia, or 

 merely traversed, as in Scleroderma, by veins of a different 

 aspect, calling to mind the peridia of JEtlialium, and other 

 compound Myxogastres. Though these plants exhibit a fleshy 

 texture when immature, or rather a crumby aspect, like that 

 of the inside of a loaf, as they advance to maturity, the whole 

 aspect is changed. The hymenial walls dry up, the threads 

 with which the cavities were traversed remain, and the whole 

 forms a mass of dust and filaments, staining and polluting 

 everything with which it comes in contact. It is rare that 

 there are definite characters about the flocci ; but in Mycenas- 

 trum the threads are far more highly developed than usual, 

 and present upon their branches spinelike processes. The spores 

 in the first instance are seated on the tips of quaternate 

 spicules, which grow at the ajDices of the component cells of 

 the hymenium or sporophores, a structure which was first 

 pointed out by Vittadini, and afterwards more fully described 

 by myself in the Annals of Natural History. After the 

 hymenial surface has dried up, they either retain the spicules, 

 or are entirely stemless. In Lycoperdon, they are for the 

 most part extremely minute, and are either smooth or finely 

 echinulate ; but in Scleroderma and Polysaccum, they acquire 

 a larger size and more varied surface. In Mycenastrum, the 

 walls of the peridium acquire a considerable thickness, being 

 in some cases as thick as an ordinary shoe-sole ; and a similar 

 structure obtains in one species, at least, of Scleroderma, in 

 Avhich the peridium splits at maturity in a stellate manner, as it 

 does sometimes in Mycenastrum. Where the peridium is double, 

 and the outer walls are thick and coriaceous, while the inner 

 are thin and membranous, we have, as in Gerister, a complete 



