240 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



a state by their presence. Such species are, in fact, true 

 epiphytes living at the expense of the plants on which they 

 are developed and flourishing, while they flourish, though 

 tending, by their presence, to exhaust the plant which bears 

 them, and causing the destruction frequently of the parts to 

 which they are attached. The whole tribe of rusts and mildews 

 is a pregnant example. In annual plants, the quality and 

 quantity of the seed are often very materially affected, if it is 

 not altogether destroyed ; and even in larger perennial plants, 

 as in the Junipers and Evergreen Beeches for instance, there 

 are parasites which spring every year from the old mycelium, 

 which end in the total destruction of the branches on which 

 they grow. In some instances the plant is deformed by the 

 presence of the parasite, and this deformation involves the 

 organs of fructification ; and as the cereals beyond all other 

 plants are subject to such affections, the injury is duly estimated 

 by the cultivator. 



231. The only remaining character, which is a negative one, 

 is, I believe, without exception. At least, I am not aware of 

 any, though it is occasionally matter of doubt, whether some 

 particular production be a Fungal or Lichen, in consequence 

 of the absence of gonidia.* In our present state of know- 

 ledge therefore, though such absence may not be positively 

 conclusive against a particular production belonging to the 

 Lichens, it is absolute as regards Fungi. Indeed, there is 

 not a single instance amongst the latter, in which a pure 

 vegetable green occurs. Green tints are by no means com- 

 mon, but when present they always approximate to mineral 

 shades. Agaricus ceruginosus, Peziza wruginosa, &c., are 

 familiar examples. The Russulce, which display the greatest 

 variety of colours even in the same species, are never of a 

 pure green, a tint which is characteristic of gonidia. 



232. The terms of our definition then being thus explained, 

 we can proceed to some general remarks on this very impor- 



* The nearest approach to gonidia occurs in a very curious genus, 

 transmitted to me by my son, from Secuuderabad, to which I have 

 given the name of Emericella. It will be noticed in a futui-e page. The 

 bodies which resemble gonidia are not, however, green. 



