36 



The Naturalist. 



celled alg£B, and on the other hand between the filamentous layer of 

 lichens and the tissues of many fungi, and between the structure of 

 the fruit in lichens, and in those fungi which have their spores 

 contained in asci, certain very advanced German botanists have 

 started the wild hypothesis that lichens are not a distinct order of 

 plants at all, but fungi, which enclose within their substance lowly 

 organized algee — the gonidia — and detain them as slaves, to provide 

 their captors with nourishment by decomposing the carbonic acid of 

 the air. 



Fungi consist of two elements — the vegetative structure, and the 

 fructification. The vegetative structure, or mycelium, is made up 

 of long interlaced thread-like cells, which penetrate the decaying 

 substances from which they draw nutriment. In the mushroom this 

 part of the plant may be found as a white, cottony-looking substance, 

 penetrating the earth around the bottom of the stem : while what we 

 call the mushroom is really not the whole plant, but only the fruit. 

 The fruit in the simplest fungi, as moulds, consists merely of spores 

 borne on the ends of the threads ; in the larger and more complex 

 fungi, the spores are produced from a special fertile layer, called the 

 hymenium (in the mushroom forming the radiating gills or plates 

 underneath) ; this is borne on a fleshy receptacle made up of com- 

 pacted filaments. There are two main divisions of the fungi : in the 

 first the spores are borne free either on the surface or in the interior 

 of the receptacle ; in the other the spores are borne, as in lichens, in 

 sacs or cells, called asci. The number of spores produced is very 

 vast, and fungi have, in addition, other means of propagation — as 

 conidia, which are powdery excrescences something like the soredia 

 of lichens. Indeed so varied are the stages in the life history of the 

 fungi, that the progress of research is continually tending to lessen 

 the number of species, by showing that what had been thought to be 

 distinct kinds, belonging even to different families, are really only 

 different conditions of one and the same plant. 



Algse differ vastly in form and size ; many are microscopic, con- 

 sisting, like the red-snow plant, of a single cell ; while on the other 

 hand some of the seaweeds attain a large size, those forming the 

 great floating masses called Sargasso Cof tropical seas) being among 

 the largest known plants. The algae are classed in three divisions, viz : 

 the red, the brown, and the green, the first two being exclusively 

 marine, while the green forms are many of them found in fresh 

 water. All the varied hues of colour depend upon the presence of 

 varieties of chlorophyll, by the possession of which algae are distin- 



