PRKLIMINAUY OBSERVATIONS. 3 



What then, generally speaking, arc the plants comprehended 

 under this denomination? Now it is very difficult to give a strict 

 definition which will comprise every individual genus and spe- 

 cies of the whole group. It would lead me into discussions 

 far too deep at present, to enter into the reasons of this diffi- 

 culty ; nor could they be understood Avithout some previous 

 knowledge of the neighbouring tribes of Lichens and Algae, 

 which I am not at liberty to assume,'* or indeed of the inti- 

 mate relations which exist generally between contiguous groups 

 of organized beings, insomuch that it is often extremely diffi- 

 cult to distinguish even a plant from an animal. It is prin- 

 cipally amongst microscopical objects that such perplexities 

 occur, though a few cases of difficulty arise where the true 

 position of a plant cannot at once be obtained from the mere 

 habit, without attention to the nature of the fruit.f 



Without any strict definition then at present, I shall pro- 

 ceed to call attention to a few of the various plants comprised 

 in the study of Mycology, from which something like a gene- 

 ral notion of the subject-matter may be gathered. 



If we take the common Mushroom (Plate 10, fig. 2) as our 

 point of departure, we have the type of an enormous group, 

 characterized by a hat or bonnet-shaped receptacle (pileus), 

 supported by a stem, and fnrnished beneath with a num- 

 ber of gill-like plates {lamella:), which deposit, when placed 

 on paper, a vast quantity of dust-like bodies, to which, though 

 reproductive, the name of Spores (Plate 1, fig, 1. a.) has been 

 given, to distinguish them from seeds which contain an embryo, 

 while these consist of a two-coated cell, M-ithout the slightest 

 trace of an embryo. These spores are of difterent colours in 



* The whole question is discussed in Berkeley's ' Introduction to Crypto- 

 gamic Botany.' 



t As in the gelatinous matter so common on gravel walks after rain, called 

 Nostoc, which has the hahit at once of a Lichen, Alga, or Fungus. 



B 2 



