LIFE OF THE PLANT-CELL. 115 



In the works of our first botanists we meet with such propositions as 

 this : " The vessels of the stem which belong to this system are the 

 expressions of the two foci of the ideal ellipse of the true peripheric cir- 

 culating system. The one abside conducts towards the light, .... the other 

 abside carries the diagonal of the former in an opposite direction into the 



darkness " Words like these are so entirely without meaning, that 



one scarcely knows what to say to them. But when once the reins of a 

 sound method are broken, there is no stopping short of the most absolute 

 nonsense, the writer not even having the least suspicion of it. Almost 

 every page that has been written on the milk-vessels exhibits proofs 

 of superficial observation, unbridled fancy, unscientific physical notions, 

 &c. The whole idea of a universal intercommunicating system of vessels 

 throughout the plant (" a cell with multifarious ramifications through the 

 plant, but closed in itself," Meyen) is purely visionary (how could the 

 few little sections, taken from a plant upon which observations are made, 

 afford foundation for a notion of this kind ?) ; but writers have been sa 

 deeply smitten with it, as to have adduced it as the fruit of observation 

 with the utmost coolness. Up to the present time, a motion of the milk- 

 sap has been noticed in only two or three uninjured plants ; and even in 

 these instances only by the direct light of the sun, observations made with 

 which are so open to optical illusion : from them, however, a universal 

 circulation is boldly deduced, and its direction, even through the entire 

 plant, described with the utmost precision. The escape of the sap from 

 cut portions is viewed as a decisive proof of its motion in the uninjured 

 part. Does not the wine in a cask also move as it runs out, when the tap 

 is turned and the equilibrium which had hitherto existed is destroyed ? 

 " The sap is expelled only by a vital action, otherwise it would be 

 retained by capillary attraction," say others. But do those who make this 

 assertion know what capillary attraction is ? Unyielding walls are essen- 

 tial to it, but not thin membranes in a turgescent tissue. Do they know 

 how capillarity acts? that it exhibits a determinate relation to the size 

 of the tube, the nature of the material of which the tube is composed, and 

 the mutual relations of the fluid and tube towards each other; and also 

 that it exists as capillary elevation or capillary depression ? Have they 

 measured the diameter of the latex-vessels, and determined the capillary 

 force of the substance composing the tubes and of the fluid, and from 

 these data calculated their capillarity ? Oh! no, it is much easier to 

 weave vain fancies than to make accurate measurements and precise cal- 

 culations ? What is the amount of the flow, then, from a stem when 

 cut across ? Very little ; and it is necessary to make a fresh section to 

 procure another flow of sap, and so on. In this case it would not be 

 wholly improbable that the capillarity should actually retain some of the 

 sap after the escape of that portion of it which could not be thus retained. 

 But in every case, however the escape is effected, leaving out of view 

 the actual motion of the sap in uninjured plants, by the turgescence of 

 the contiguous cellular tissue; and this cause must always be first taken 

 into account. It explains, for instance, very readily, the reason why more 

 sap escapes from the upper end of a cut stem than from the] lower ; 

 because the younger cells, with more yielding walls and more distended 

 with fluid, must necessarily enlarge more than the more closely united, 

 older, and thick-walled cells in the lower portion of the plant. Argu- 

 ments of this kind might be multiplied to a great length, but what I have 

 observed is sufficient to show how very superficially this subject has been 

 treated. It is by no means my intention in this way to prove the non- 



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