65 



tendency of the cells to retain as much of the globular form 

 or to return to it as nearly as the reciprocal pressure, &c. al^ 

 low, is very apparent. 



This supposition, however, requires at least, that those cells 

 of the parenchyma of the Riccics should be in their origin 

 spherical, and have been subsequently compressed. But can 

 this be observed in the RICCICB ? I think I may answer the 

 question negatively, for in the Marchantice where the cellular 

 tissue is exactly similar to that in the Riccice, it may be ob- 

 served that the development of the form of the cells is not 

 effected in the way above described. The mathematical deve- 

 lopment of Kieser's hypothesis on the origin of the form of the 

 cell is nevertheless quite correct, and even Stephen Hales de- 

 monstrated very decidedly that round bodies of uniform size, for 

 instance common peas, when caused to swell in a firmly closed 

 space filled with them, were changed by reciprocal pressure 

 into dodecahedrons. This form, produced by external circum- 

 stances, cannot however be regarded as the ideal primitive 

 form of those originally round bodies; and it is founded on 

 very erroneous observations, if it be supposed that the ideal 

 rhomboidal dodecahedral cells can round off at their edges 

 and corners and pass into the various other forms. If the re- 

 ciprocal pressure ceases, which sometimes, from the unequal 

 expansion of certain parts, occurs, the separated cells re-as- 

 sume the spherical form from which they had departed. 



M. Lindenberg has given a very detailed account of the sub- 

 ject in question, in which we find the following observation ; 

 " that in sections of cellular tissue other forms besides the 

 hexagonal occur, which does not prove against, but in favour 

 of Kieser's view," i. e. that the form of the cells is that of 

 the rhomboidal dodecahedron. However I have only been 

 strengthened by continued observations in my views on this 

 subject (see Phytotomie, p. 216.), nay, I could at present bring 

 forward more detailed observations than at that time. And, in 

 fact, it is surprising, that even now mention is made in many 

 manuals of botany, of the rhomboidal dodecahedral form of the 

 cells, whilst good longitudinal and cross sections place the true 

 form of the cells immediately before the eye; I will also mention 

 that cells of the continuous parenchyma whose form resembled 



