242 INTRODUCTION TO CRTPTOGAMIC BOTANY. 



the shape of roots, and the spores will always spring directly 

 from the threads, or be formed within the threads, at the ex- 

 pense of the endochrome. It is very true that the yeast plant 

 may be indefinitely increased by constant pullulation of free 

 floating cells, without a trace of rootlets, and for this reason 

 it has been considered as an Alga. But as it has been proved 

 by myself and Mr. Hoffman,* by following up the development 

 of individual yeast globules in fluid surrounded in a closed 

 cell with a ring of air, that the proper fruit is that of a Penicil- 

 liwm, and as this Penicilliwm has, on more than one occasion, 

 been observed to grow on fermenting matter, it is quite clear 

 that yeast is merely an abnormal state of a Fungus, very differ- 

 ent in habit, and forced into a peculiar mode of development 

 by its submerged position. I believe equally that Sajyro- 

 legnia and Achlya mentioned above (p. 132), with their active 

 zoospores, are mere submerged states of species of Mucor. 

 There are, besides, a whole host of myceha produced in vege- 

 table and mineral infusions referred to A] gas, which are nothing 

 more than submerged confervoid forms of species of Peni- 

 cillium and Aspergillus, very commonly of the two most 

 ordinary kinds. In general, however, simple in structure as 

 the lowest may be, and there are many that apparently consist 

 only of a single cell, there is, as said above, a more or less 

 apparent system of threads or cells (mycelium) from which 

 they spring, traversing frequently the tissues of the matrix, 

 and discoverable only by close microscopic investigation ; and 

 even if there be cases where no mycelium exists, a fact of which 

 I very much doubt the reality, or even the possibility, though 

 the mycelioid system may be reduced to an extremely low 

 degree of development, there is usually a definite arrangement 

 of the spores, a point very easUy recognised, except in the very 

 rare cases in which, by repeated division, they are apparently 

 indefinite. The fact, indeed, is, that in the greater number 

 of Fungi, the fruit bears a very high proportion, indeed, 

 to the vegetating part or mycelium. But the enormous 

 pileus of the Horse Mushroom does not bear a larger ratio to 



* See Article Yeast, in Morton's Cyelopsedia of Agriculture. 



