2 
ORGANOGRAPHY. 
BOOK I. 
It is the opinion of some that membrane only is the basis of 
the tissue of plants, and that fibre is itself a form of mem- 
brane. But as we find both developed in many of the most 
imperfectly organized plants, such as Scleroderma and other 
fungi, and as it is difficult to conceive how that can be a 
mere modification of membrane which is generated inde- 
pendently of it, which has no external resemblance to it, and 
which is obviously something superadded, it will be better to 
consider both membrane and fibre as the organic bases of 
vegetable tissue, rather than the former only. 
The membrane varies in its degree of transparency, being 
occasionally so exceedingly thin as to be scarcely discover- 
able, except by the little particles that stick to it, or by its 
refraction of light, and sometimes having a perceptible green 
colour, and a thickness which is considerable if compared 
with the diameter of the cavity it encloses. It is always ex- 
cessively thin when first generated ; and whatever thickness it 
afterwards acquires must be supposed to be owing to the 
incorporation or incrustation of secreted matter. This is 
represented by Mohl to take place in Palm-trees by the succes- 
sive addition of strata to the lining of the cavities of the cells ; 
but this requires verification. 
It generally tears readily, as if its component atoms do not 
cohere with greater force in one direction than another ; but 
I have met with a remarkable instance to the contrary of this 
in Bromelia nudicaulis, in which the membrane of the cuticle 
breaks into little teeth of nearly equal width when torn. 
(Plate I. fig. 6.) Hence it maybe conjectured, that what we 
call primitive membrane is itself the result either of primitive 
fibres completely consolidated, or of molecules originally dis- 
posed in a spiral direction, as Raspail supposes. (Chim, Org. 
P.85.) 
It is in all cases destitute of visible pores ; although, as it is 
readily permeable by fluids, it must necessarily be furnished 
with invisible passages. An opinion to the contrary of this 
has been held by some botanists, who have described the 
existence of holes or pores in the membrane of tissue, and 
have even thought they saw a distinct rim to them ; but this 
idea, which probably originated in imperfect observation with 
