HORTICULTURAL JOURNAL. 271 



Rhododendron leaf, 150 on that of the Oat, &c. More than three millions 

 have been counted on a single leaf of the above mentioned Iris. 



But, however important those pores may be, certain it is that it is not 

 by those parts exclusively that the communication of the exterior world 

 with the interior of the plant is entertained. We are sure that each mem- 

 brane of plants, and consequently also that which lies on the surface, 

 possesses the property of admitting fluids, of whatever nature they may be, 

 without the presence of determined openings, though the conditions which 

 are required for it are not always known to us. It is a fact that the whole 

 surface exhales or respires — takes up fluids and conveys them to the inner 

 part of the plant. 



In order to make our further contemplations useful to our readers, we 

 have been obliged by these observations, to introduce them into the structure 

 and nature of plants. 



It may be accepted as a truth that the vesicles or cells of the root may 

 be at all times active, in a greater or less degree, even independent of what 

 takes place in the other part of the plant which is above the soil. The 

 "endosinosis," such is called the property of the cells (which contain 

 thicker fluids) of taking up thinner ones — the endosmosis, that peculiar 

 faculty of absorbing, takes place during the colder seasons as well as in the 

 summer in the cells of the roots, and also in more inwardly situated cells. 

 In other words, where there is life there must be movement also. The 

 movement which takes place here, consists of the exchange of fluids from 

 one to another cavity of cells. That movement and the supply and 

 exchange of substances which it necessarily brings about, is the only cause 

 of the growth. It must, though in a less degree, take place in the parts 

 under ground, even when the cold of the winter stops all growth and develop- 

 ment — when the superficial contemplater does not see in nature the least 

 trace of life. The following causes will explain how this is possible. 

 When the earth seems to be changed into a crust of ice, the temperature of 

 the ground at a relatively small depth is higher than that of the air. It 

 has been proved by experiments, that the temperature of the interior of 

 trees is different from that of the surrounding atmosphere. It has been 

 observed that even at periods when the thermometer has fallen below the 

 freezing point, and thus when the air is cold, when water becomes ice, the 

 inner part of the trees is warmer. Incisions were made in the trunks of 

 trees in winter, thermometer-bulbs were inserted, and the quicksilver therein 

 was some degrees higher than in that of thermometers hung up near the 

 trees in the open air. The trees retain their proper degree of heat, not- 



