INTRODUCTION 



day, when other and improved methods have been brought into 

 use. Instead of the term Thallogens for the cellular Crypto- 

 gamia, it would be preferable to call them Thallophytes, and, 

 for the rest, Bryophytes would include Mosses and their allies, 

 whilst Pteridophytes would be represented by the Ferns. 



Thallophytes, in a general sense, which will be sufficient for 

 practical purposes, consist of those plants which grow in water, 

 and obtain their sustenance therefrom, commonly known as 

 Algae ; and those which flourish in the air, being sustained by 

 the decomposition of the matrix on which they flourish, as 

 Fungi ; or drawing their sustenance from the air, and rarely, or 

 but slightly, from the matrix, as in Lichens. Here again a 

 negative feature may be interposed with advantage, to the 

 effect that Lichens are not of a fleshy or putrescent, but of a 

 dry and leathery consistence, whereas in the bulk of Fungi 

 the substance is, either entirely or in the early stage, soft and 

 fleshy, becoming indurated or putrescent with age. The 

 distinctions between Algae and Fungi will never cause any 

 practical difficulty, because the Saprolegnieae, which are 

 aquatic, and approach Algae most nearly in habit, derive their 

 sustenance from the matrix on which they are parasitic by 

 means of penetrating mycelial threads, whereas Algae are 

 simply attached by root-like or sucker-like extensions to the 

 matrix, from which nothing is absorbed. The relations between 

 Fungi and Lichens are much more intimate, and in extreme 

 cases approach each other so closely as to be distinguished 

 with difficulty even by experts. Whole genera are still 

 claimed by mycologists on the one hand, and by lichenologists 

 on the other. Still it must be remembered that these are 

 extreme cases, and that amongst the larger Fungi, especially in 

 the great group of Hymenomycetal Fungi, there is but little 

 suggestion of Lichen affinity except in such genera as Cora, 

 Dictyonema, Pavbnia, etc. Another exceptional case may be 

 found in the Nostoes, which are Algae, simulating or so closely 

 resembling Tremella, a genus of Fungi, that microscopical 

 examination may be necessary for their discrimination. 



Habitat may in some cases serve to indicate the character 

 of the Thallophyte. For instance, all the parasites on living 

 leaves which are not of insect origin are Fungi, such as the 



