46 WENHAM, ON THE SAP-CIRCULATION OF PLANTS. 



sap-currents extend the entire length of the cells or hairs, and 

 in others they are divided into an irregular network of ramifica- 

 tions, which shift their positions with considerable celerity, the 

 diversity of the phenomenon, perhaps, depending in some 

 measure, upon the constitution and fluidity of the sap, for 

 where this is rather glutinous the current traverses in the 

 form of a sluggish uniformly moving sheet or layer, lining 

 large portions of the interior of the cell ; I may mention hairs 

 from the Elder {Sambiicus 7iiffer) as an instance of this. 



In all cases where the sap-motion is seen in the hairs of a 

 plant, the leaf-cell displays analogous peculiarities, provided 

 the cuticle is not too opaque, or strongly marked to obstruct 

 vision. The cells are best obtained, by tearing off a layer of 

 the cuticle from the stalk or midrib of the leaf, and must then 

 be examined as speedily as possible, for the specimen loses 

 its vitality much sooner than the hairs. There is scarcely a 

 portion of a leaf-cuticle possessing the requisite trans- 

 parency, taken from any plant wherein I have not discovered 

 indications of circulation ; even where there is no direct 

 motion of particles to be seen, on account of their minuteness, 

 the existence of circulation may still be known, from the fol- 

 lowing fact : — The active corjMscles, which are the primary 

 cause of all the circulatory movements, are remarkable for 

 their high refractive power, both on their completion, and in 

 different stages of formation, and when arranged in a moving 

 train, they appear as bright lines across the cell.* 



Many specimens of leaf-cuticle, in which at first no move- 

 ments whatever can be discovered, exhibit these lines, which 



* As these observations were intended to be exclusively confined to the 

 sap-circulation, I have been desirous of recording them in the simplest 

 manner possible, and have therefore avoided technical expressions ; what 

 I have termed " the investment of active corpuscles," has been known 

 as " protoplasm," or " cell-mucus." It may be doubted whether these 

 terms are strictly applicable, or truly represent that which in reality 

 consists of a multitude of particles, possessing individual activity and 

 differing in size, and probably in chemical constitution, according to local 

 position and the variety of plant-substance and tissue with which they 

 are ultimately destined to combine, such as cellulose, and the loose con- 

 tents of the cell, as chlorophyll- and starch-granules, the latter being most 

 evidently formed by the successive deposit of external layers upon a 

 central nucleus. 



I may also remark, that it was formerly supposed, and some even now 

 retain tlae same opinion, that the " circulation," " rotation," " gyration," 

 or " cyclosis," in the vegetable cell, both in its early development, or 

 growing stages, was in some way connected with a central nucleus, also 

 kept in rotation, and termed the " cytoblast." I consider this supposition 

 to be entirely fabulous, for whenever I have occasionally observed such a 

 nucleus, it has either been formed by an accidental conglomeration of some 

 of the cell contents, or by morbid conditions. 



