Dr. A. de Bai-y on the Mycetozoa. 235 



deficient of colouring matter in their cells; but, like the Sipho- 

 uaea, they are inhabitants of water, and, what is more, they 

 possess zoospores, which have never yet been discovered with 

 certamty m any Fungi. 



In structure and development the Fungi are closely related 

 to the Lichens. The only appreciable difference between them 

 is that the hyphae composing the thallus of the latter are sepa- 

 rated by a distinct layer ("gonidial layer ^^ of chlorophvll-bearing 

 cells, probably concerned in the process of reproduction. In the 

 matter of Iructification there is an exact similarity between the 

 Lichens and a large grou]) of Fungi, and lastly, these two classes 

 ot organisms approach likewise generally in the mode of nutri- 

 tion. In short, so intimate are the relations between the two, 

 that iierkeley and others have proposed to unite them as tuo 

 orders m one class. 



The Fungi, as a definite class of organisms, agreeing among 

 themselves in habits of life, in histological elements and in the 

 phaenomena of development, are separable from certain struc- 

 tures commonly referred to them on account of the similarity 

 in their habits and mode of nourishment, represented by the 

 greater portion of the Mycophycese. Among these pseudo- 

 l^ungi are the moulds or mildews that form on decomposing 

 substances, the relations of some of which are readily determin° 

 able, whilst others are only incompletely develoi)ed jihases in 

 the cycle of develo]mient of true species of Fungi. 



The formation of the sjiores of Fungi proceeds in a threefold 

 manner: 1. The spores are produced, singly or several together, 

 by the division of the terminal or twig-ccll of the hyphie (the 

 basidia) ; or, 2. such cells swell into vesicular sacs (asci), from 

 the contents of which the spores are developed by free-cell 

 formation; or, 3. one of the cells, usually the terminal, divides 

 into two or many spores, which become secondary cells (daughter- 

 cells . More complex methods of fructification occur in the 

 basidia of Tremeik, and in the spore-cysts (sporothecje) of Eu- 

 rotium, Erysiphe, as the result of a combination of two of the 

 three primitive types. 



Sexual development is not yet demonstrated, although ren- 

 dered not improbable by the researches of Ehrenberg on the 

 conjugation of Sijzijijites. 



The systematic distribution of the Fungi has hitherto been 

 founded primarily upon their modes of development, and in a 

 secondary degree upon the dispositi(m and structure of the 

 spore-cells. But, as Tulasne has latterlv proved, one and tlie 

 same species may exhibit the several modes of fructification 

 At the same time, it must be granted that the actual state of 



16* 



