CKIPTOGAMIA. 411 



nemia, which they caused to spring from certain parts of the asexual 

 plant. This discovery stands in much the same relation to the 

 alternation of generations in the Muscinece as the discovery of Mr. 

 Farlow does to that of Vascular Cryptogams. There are, besides, 

 different modes of vegetative reproduction in Mosses, the principal 

 of which are by gemmae and by stolons. 



Thallophyta. We now come to the lower Cryptogams called 

 Tlmllopliyta, under which name are comprehended the Algse, 

 Fungi, and Lichens. The vegetative structure is in the greater 

 number of cases a simple one, since the plant usually consists of 

 a thallus in which no distinction between root, stem, or leaf exists. 

 The class includes organisms, however, of widely different degrees 

 of development. The lowest forms are composed of one cell, and 

 often bear so strong a resemblance to the minute animals called 

 Infusoria, that it is only in recent times that a satisfactory division 

 has been established. By almost imperceptible gradations we rise 

 to the highest representatives, in which indications of those forms 

 called leaf and stem appear and an undoubted differentiation of 

 tissues exists. The functions of a root, when such are necessary, 

 are performed by root-hairs, and by a kind of sucker called a 

 Jiaustorium in those plants which live by parasitism. The class, from 

 its comprehensive nature, includes an extraordinary number of 

 forms, which can, however, usually be distinguished into a com- 

 paratively small number of groups. In their life-history Thallo- 

 phyta cannot be brought under one general rule, as in the case of 

 the Cormophyta. In many cases a simple alternation of genera- 

 tions is the rule, while in others several generations form a life- 

 cycle, links of which may, under circumstances, be omitted ; but this 

 is the exception. In the Uredinece, for instance, three generations 

 form the life-cycle of the plant. 



FUNGI. In the Fungi the vegetative body consists, with the 

 exception of several doubtful cases, of filiform, more or less 

 branched hyplice or threads. In many instances the thread is one 

 long, densely ramifying, bladder-like cell; but in most cases it 

 consists of a series of cells placed on end wdth dichotomous or 

 lateral branches. Of such cells the large bodies of our familiar 

 Fungi, as well as those of the minute species, are composed. The 

 cohesion of the hyplice is usually effected by their being densely 

 interwoven in various ways in the different plants. It must, how- 

 ever, be mentioned that exceptions to this very general condition 

 of things exist. There is found in the stalks of the Phalloidece, 

 in the pileus of 2iussula, Lactarius, in Sclerotia, and in the 

 peridia of the Lycoperdacece a kind of tissue bearing a resem- 

 blance to the parenchyme of the higher plants ; but this resemblance 



