THE CELL-THEORY 255 



for granted, and if they were untrue he has been trusting to a rotten 

 reed. Such, we fear, has indeed been the case. Schwann's botanical 

 data were : 



1. The prevalent notion of the anatomical independence of the 



vegetable cell, considered as a separate entity. 



2. The prevalent conception of the structure of the vegetable cell. 



3. The doctrine of the mode of its development. 



Each of these, as assumed by Schwann, and as taught by Schleiden, 

 has since, we shall endeavour to show, been proved to be erroneous. 

 We will take them seriatim. 



I. The first observer who, aided by the microscope, turned his 

 attention to the structure of plants, was the versatile Hooke, and, as 

 might be expected, the most noticeable thing to his mind was the 

 existence of the innumerable cavities or " cells ' scattered through 

 their substance. Malpighi, the first proper botanical histologist, found 

 that the walls of these vesicles were separable, that they could be 

 isolated from one another, and therefore, doubtless urged more by the 

 obvious convenience of the phraseology, than by any philosophical 

 consideration upon the subject, he gave each the definite name of 

 " utriculus," and regarded it as an independent entity. Of course it 

 was a natural consequence that the plant should be regarded as con- 

 stituted by the union and coalescence of a great number of these entities. 

 Grew, who if all scandal be true, is so much indebted to Malpighi, did 

 not appropriate this view among other things ; on the other hand, he 

 compared the utricles to the cavities in the foam of beer ; and subse- 

 quently Wolff propounded the idea, that the cells were cavities in a 

 homogeneous substance, as we have mentioned above. In modern 

 times, the most important defender of this mode of regarding the 

 matter has been Mirbel, who (escaping the error of Wolff, that the 

 cavities of the cells communicate) endeavoured to demonstrate its 

 truth, by tracing the formation of the cambium ; but, at the time when 

 Schwann wrote, it must be considered to have been wholly discredited, 

 the opposite view having one of its strongest supporters in the caustic 

 Schleiden himself — as, indeed, would necessarily be the case, from the 

 tendency of his researches upon phytogenesis. As we shall see below, 

 however, Schleiden was quite wrong in his ideas of cell-development — 

 and we have therefore merely to consider the purely anatomical argu- 

 ments for the independence of the cell. Now these amount, however 

 various their disguise, to nothing more than this — that, by certain 

 chemical or mechanical means, a plant may be broken up into vesicles 

 corresponding with the cavities which previously existed in it : of 



