LIFE OF THE PL ANT -CELL. 87 



alkaloids are found united to the organic acids. 2. Bodies such as 

 tannin, resin, &c., are frequently formed which have a great affinity 

 for oxygen, and thus from the vicinity of the cell absorb a con- 

 siderable quantity of this gas. 



There is more need perhaps of research on these subjects than those 

 of preceding paragraphs, but yet sufficient is known to impress us with 

 the fact that all depend on physico-chemical processes. The great in- 

 security here arises from the deficient knowledge we possess of the rela- 

 tion of these substances to the so-called indifferent bodies. We know 

 that starch, sugar, &c. are composed of so many atoms of carbon and 

 water, but not how they are actually formed, or how they originate from 

 their elements. 



Above I have divided the secretions from the assimilated matters ; and 

 though some of the former should ultimately be placed among the latter, 

 it will not affect the propriety of this division. We might here classify 

 these secretions according to their greater or less extension throughout 

 the vegetable kingdom ; but such an arrangement would have no relation 

 to the processes of life in the plant-cell, and therefore would be super- 

 fluous in this place. 



Two points must be noticed here. The cells take up with the water 

 various salts. A part of them are inorganic, a part organic. Of the first 

 a part, perhaps, remain in the cell from the evaporation of the water. 

 Another part are decomposed in manifold ways through the chemical 

 processes which go on in the inside of the cell. From these are pro- 

 duced new bodies, which again decompose each other, and act upon those 

 bodies already formed ; and thus the whole of the processes become more 

 complicated. A part of the salts seem also destined for the neutralisation 

 and removal of the acids produced by necessary processes. The pre- 

 sence of a large quantity of oxalate of lime in the Cactacece is thus 

 explained, the injurious oxalic acid which is formed in the cell being 

 united to lime, which is taken up from without in the form of a soluble 

 carbonate of lime, and an insoluble and innocuous salt is thus formed. 

 Liebig* has given an opinion that a certain quantity of bases appear to 

 be constant, in every plant, in every locality. Perhaps, they are those 

 which the plant cannot do without to bring its chemical processes into 

 equilibrium. A similar equilibrium may be found between some of the 

 substances which are injurious, and formed in the cell, and which united 

 together form perfectly harmless bodies. 



The substances which are formed in the cell, and which have a great 

 affinity for oxygen gas, will take up this substance from without the cell, 

 provided it is not supplied them from within. This is easily effected, as 

 the experiments of Dalton and Graham show that a moist membrane is 

 no hindrance to the penetration of a gas. In this way an absorption of 

 foreign substances originates which is entirely independent of the pe- 

 culiar nutrition of the cell. It may be a question as to whether other 

 gases, as, for instance, carbonic acid, are not taken up into the cell in this 

 manner. It is very certain that through this oxidation the substances 

 are thus brought into a new relation with each other, and a new play of 

 chemical activities is introduced. 



* Organische Chemie, p. 85. 

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