Sketch of the Class Fungi. 109 



TricMcB they are at first quaternate, and end by becoming isolated. 

 Some are supported by a pedicel*. After having partaken in their 

 youth of the mucilaginous nature of the medium, they harden by 

 degrees, and undergo with this change of consistence a sort of de- 

 formity. Thus, from being spherical, they assume, by a lateral 

 contraction, the form of a grain of coffee or wheatf (e. g. Stemo- 

 nitis). They are, however, always simple when mature, and com- 

 posed of a single membrane or epispore, and of a homogeneous or 

 heterogeneous nucleus. A great number of the species have sporidia 

 in which are traces of a hilum, a persistent testimony that they 

 were at first attached to a filament performing the functions of an 

 umbilical cord. 



Fries has established in this section two grand divisions, founded 

 upon the colour of the sporidia, naming those in which they are of 

 a dusky hue, like that of soot, ligneospermce, while those whose spo- 

 ridia are of a more attractive tint he calls calospermce. 



The metamorphosis of Myxogastres is a work of Nature as mar- 

 vellous as it is incomprehensible. It takes place frequently in a few 

 hours J, and the observer can easily watch all its phases. It is 

 matter of regret, however, that their fluxile nature never allows us 

 to follow step by step the development of the inner parts, as we 

 shall see that we are able to do in the Angiogastres and Tricho- 

 gastres. 



These fungi grow and multiply under certain meteoric circum- 

 stances : the ligneospermcB, which are very fugitive, on various orga- 

 nized bodies, even on rocks ; the calospermce constantly on the trunks 

 of dead trees or rotten wood. The first appear only at certain times 

 and in certain seasons ; the latter, being less meteoric, appear indif- 

 ferently in all. As regards their geographic distribution, as the 

 essential conditions of their growth are moisture combined with 

 heat, we may admit with Fries, that they have their centre in the 

 temperate zone, without however excluding the tropics, where, 

 though less common perhaps, they are by no means absent. I have 

 received from Brazil, Chili, and Cuba, species identical with those 

 of our continent. 



The primitive mucilage or medium of the Myxogastres, arrested 

 in its morphosis by dryness or any other cause, is frequently indu- 

 rated, and remains a long time in the form of coloured veins, which 

 have given rise to the genus Phlehomorpha, Pers., or sometimes 

 simple hemispherical substances, which on account of their consist- 

 ence have been regarded as Sclerotia. 



This is the proper place to advert to the Sclerotiaceee (referred at 

 first by Fries to Coniomycetes), and in particular to tlie typical genus 

 Sclerotium. He formerly considered the species of this tribe as formed 

 of a fleshy, very hard stroma, on the circumference of which the 

 sporidia originated. More recently he has regarded the outer en- 

 velope as a true peridium, and in this he has been followed by Corda 



♦ Corda, I. c. i. t. 6. f. 288**. 



t They recover their original form when placed in water. — M. .). B. 



X See Ann. d. Sc. Nat. Nov. 1841, p. 308, under Trichamphora. — M.J. B. 



