Meyen's Report for 1839 on Physiological Botany. 271 



case of ammonia, and hence it is quite comprehensible why 

 nitre mixed with the soil in proper quantities is so highly 

 advantageous. The idea of the most celebrated chemists, that 

 most vegetable substances require only carbon, hydrogen, and 

 oxygen to their formation, and that beside these nitrogen is 

 only necessary for some certain classes of bodies, is held by 

 the author to be erroneous ; for he assumes that gluten, legu- 

 min, &c. contain lime, phosphoric acid, sulphur, &c, besides 

 their usual ultimate constituents, and that these substances 

 (gluten, &c.) cannot make their appearance in the plants un- 

 less the above-mentioned inorganic bodies are combined with 

 them. Sprengel assumes also, that the woody fibres are the 



skeleton of the plant, and consist of Si, Ca, Al, Fe, Mn, C, 

 H, O, &c. ; the chemists' idea that the fibres consist of the 

 three last-mentioned bodies alone, is in his opinion quite false ; 

 for, says he, if one burns the purest possible fibres, there al- 

 ways remains a small residue of ashes consisting of the above- 

 mentioned substances. It is a pity that the author has not 

 stated more plainly what he means by " fibres vegetable 

 anatomy teaches us the infinitely great variety in the physical 

 properties of the membranes which form the cells, and he who 

 has attentively followed with the microscope the formation of 

 the deposits of new membranes, will plainly see that all those 

 inorganic matters, or a great part of them, which are con- 

 tained in solution in the sap, out of which the formation of 

 the membranes proceeds, must exist either in the substance 

 of the hardened membrane or in fine layers between the strata. 

 Here, probably, are all the inorganic substances which acci- 

 dentally enter into the sap, in larger or smaller quantity. The 

 small quantity of ashes found in starch can only be explained 

 in this manner. Perhaps, therefore, the author is in error 

 when he compares the appearance of the above-mentioned 

 matters in the cellular membrane of plants, with the deposi- 

 tion of phosphate of lime in the bones of animals, and I have 

 already (in the former Reports) drawn attention to the insur- 

 mountable difficulties in the way of the experiment, or of a per- 

 fect purification of the cells. 



The author considers dung, it is true, as the universal ma- 

 nure, but says, that sometimes even this is not sufficient, be- 

 cause it contains too little mineral matter. According to his 

 ideas, therefore, the plants in such cases were in want of the 

 true mineral manures, while, as is well known, this phe- 

 nomenon is explained by others in a totally different 

 manner. 



The author also states very positively that the soil can then 

 only produce good crops, when it is provided with the neces- 



