PAET I. 



Phenomena op Vegetation on which Mbteobological Effects 

 OP FoEESTS Depend. 



Chap. I. — Peihaet Phenojiena of Vegetation. 



The study of the phenomena of vegetation, on which meteorological 

 effects of forests depend, may adTantageously be begun by the con- 

 sideration of what takes place in some of the more simple forms of 

 vegetables. 



The simplest form of vegetable appears to be what is called Eed 

 Snow. In Alpine and Arctit regions, there are occasionally seen on 

 the rock or on the snow patches of red-coloured matter, not imlike 

 dust. When this matter is examined microscopically it is found that 

 each particle of the dufit-hke substance is a small ceU, or bladder-like 

 body j it is not a crystal ; it does not appear to be an ani mal ; it 

 seems to be a plant — and a plant of simpler structure it would be 

 difficult to conceive. It is known to botanists as the Protococcus 

 Nivalis. 



A plant similar to this, but somewhat more complex in structure 

 — if the term complex can be employed with propriety in speaking 

 of a structure so very simple — is seen in the Yeast Plant. 



With a stick or a spoon there may be drawn from yeast in active 

 fermentation thread-like bodies which, when examined microscopi- 

 cally, appear Uke a string of beads, each bead being a cell, not unlike 

 the Eed Snow in structure, but colourless. This is the Yeast Plant, 

 and if the thread be broken each cell may be developed into a thread- 

 like plant similar to that from which it has been dissevered. 



In Conferva, and in many confervoid plants found in streams and 

 fresh water pools, we find a similar structure, but this is enclosed in 

 an investing skin, and the cells are drawn out from a globular into a 

 more or less elongated cylindrical form. And in the larger Algae, or 

 sea weeds — some of which there are which are 1000 feet in length — 

 when they are examined microscopically we find, and find only, a 

 mass of such ceUs less regularly arranged, enclosed in an investing 

 skin of similar cellular structure. 



