146 THE PRINCIPLES OF FLORICULTURE 



the leaves. Temperature and moisture conditions should 

 also be ideal, to facilitate the action of these stomata, 

 which are to allow gases to penetrate the leaf readily. 



Kerner l describes the action of nutrient gases in 

 plants as follows : 



" As soon as carbonic acid reaches the cell sap, it is 

 decomposed and reduced by the action of the sunlight, 

 and from it are formed compounds known as carbo-hy- 

 drates. The oxygen thus set free is, however, removed 

 from the cell precincts and expelled into the surrounding 

 air or water. In this way, the gas, when barely absorbed, 

 is. withdrawn as such, from the cell sap, the carbon alone 

 being retained and the oxygen eliminated and a renewed 

 attraction of carbon-dioxide from the surrounding medium 

 ensues. The fresh supply again is immediately worked up 

 in the green chlorophyll-bodies so that there is a constant 

 influx of carbon dioxide and, therefore, indirectly of car- 

 bonic acid from the environment into the interior green 

 cells to the part where its consumption takes place. Were 

 it possible to see the molecules of carbon-dioxide in the air, 

 we should observe how much faster they are impelled 

 towards the leaves and other green parts of plants, where 

 the intense craving for carbon is localized, than are the 

 other constituent particles of the air. This impulsion and 

 influx lasts so long as the green cells are under the influence 

 of daylight. The first thing in the morning when the first 

 ray of sunshine falls upon a plant, the protoplasts begin 

 work in their little laboratories, decomposing carbonic acid 

 and producing from it, sugar, starch and other similar 

 organic compounds. And it is not till the sun sets that 

 this work is suspended and the influx of carbon-dioxide 

 stopped till the following morning." 



1 " The Natural History of Plants," Kerner and Oliver. 



