LIFE OF THE PLANT-CELL. 117 



plants, and under the most varied circumstances. Every one having 

 the slightest idea of what experiments, hypothesis, induction, and theory 

 really signify in the natural sciences, will certainly agree with me, that, 

 in the generally defective state of our knowledge respecting the physical 

 and chemical processes going on in plants, it would be altogether a 

 childish undertaking to attempt to weave a theory out of elements such 

 as these ; and any others are, as yet at least, in dispute. Let any one 

 that will have recourse to the convenient scape-goat of a universal vital 

 power amuse himself with it, but he must not imagine that in doing so 

 he is proposing any thing profound or really scientific. It is also clear 

 that we have no certain facts sufficient to afford foundation for an ana- 

 logy with the motion of the blood in animals, even allowing that this 

 analogy is any thing more than an idle and fanciful notion. 



Respecting the contents of the latex-vessels and of the other two forms 

 we know just as little. They differ specifically in almost every plant, 

 and frequently in different individuals of the same species, at least in 

 the quantity of the separate constituents. It would appear that the latex 

 pretty generally contains caoutchouc in granules, in greater or less quan- 

 tity according to the age and the manner of vegetation of the plant. 

 It also presents a great number of peculiar substances, for the most part 

 of a poisonous, at all events of a highly suspicious, nature. Of the 

 contents of the liber-cells we know nothing at all. "With regard to 

 the importance of the latex, in respect to the life of the plant, if we 

 disregard Schultz's wholly unfounded fancies, we are also entirely in 

 ignorance. Meyen*, after collecting all the cases in which the latex is 

 innoxious, and showing that, in many instances where it is poisonous, 

 innoxious substances are also found in it, concludes " that the latex 

 may be a thoroughly elaborated nutritive juice, at least as regards man 

 and animals, and therefore the assumption that it also plays the part of 

 a nutritious sap in the plant is certainly not inadmissible." It is cer- 

 tainly impossible to arrive at a conclusion more illogically. Commencing 

 with the absolutely poisonous latex of Antiaris toxicaria, Hippomane, 

 ami Exccecaria, when it is shown how frequently an innoxious latex, 

 as, for instance, that of the young lettuce, becomes poisonous as soon 

 as the plant is only in some degree perfected, how the poppy can be 

 poisoned with opium, and the lettuce with lactucarium, there would 

 appear to be much better reason for arriving at an exactly opposite con- 

 clusion. But, on this subject, the question is not at all as to inferences 

 and conclusions ; we have here to deal only with suppositions and asser- 

 tions. 



Probably all these organs, like the latex receptacles by which they 

 are frequently replaced, are for the purpose of receiving matters, and 

 preventing their reaction upon the living cells, which would otherwise 

 be detrimental to the life of the plant. This is at all events indicated 

 by the circumstance that almost all vegetable poisons, and which act as 

 such on the very plants by which they are yielded, are found in the 

 latex ; but, as yet, nothing but the most vague suppositions can be 

 broached. Liebig'sj* notion, that in plants with a milky sap the water is 

 surrounded by an impervious case of caoutchouc, and that plants in a hot 

 climate are thus secured against desiccation, arises from a complete ig- 

 norance of vegetable structure. 



* Pflanzenphysiologie, vol. ii. p. 410. 

 f Organische CbcMiiie, p. 57. 

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