SECT. I. ORGANOGRAPHY AND GLOSSOLOGY. 17 



termed " intercellular passages," and are very evident 

 in some portions of the tissue, 7 



but are not to be detected in 

 others. The forms under 

 which the vesicles appear, up- 

 on making a section through 

 the cellular tissue, are much 

 influenced by local pressure, 

 distension, and the more 

 obscure causes which depend 

 upon the specific qualities of 

 each plant ; and these forms 

 are detailed with greater minuteness, in works which 

 professedly treat of this part of our subject, in a more 

 elaborate manner than our limits will afford. 



(18.) Striated and dotted Cells. The separate vesi- 

 cles which compose the cells, frequently exhibit mark- 

 ings upon their surface, whose origin it is not always 

 easy to account for. Many of these appearances were 

 formerly mistaken for open pores through the mem- 

 brane, by which a communication was supposed to 

 subsist between two contiguous cells. Some observers 

 have considered them to be glands ; and others have 

 described them as nascent vesicles, generated within 

 the surface of the old cells, and which are afterwards 

 developed, and thus are formed into new tissue. The 

 best representations of these various appearances, is given 

 by Mr. Slack, in the forty-ninth volume of the " Trans- 

 actions of the Society of Arts ; " and he is inclined 

 to refer the greater part of them to one common origin, 

 viz. the modification of the conditions under which 

 the elementary fibre is developed on the inner surface 

 of the vesicles. In some vesicles, this fibre is spirally 

 coiled over the whole surface, and the contiguous coils 

 are blended together, so as to render it very difficult to 

 distinguish them : in others, the coils are wide apart, 

 and distinctly visible (fig. 8. a). In some cases the 

 fibre is branched (6) ; and in others, the branches 

 graft together, and the surface of the vesicle then appears 



