VEGETABLE PHYSIOLOGY*. COMPOUND ORGANS. 
25 
with lines traversing it in various directions, and which, by 
anastomosing, give to it a reticulated appearance : the most usual 
form of this reticulation is hexagonal; but it is sometimes 
marked by sinuous lines, having no determinate figure. 
On the exact nature of the cuticle botanists are not agreed: 
some incline to the opinion that it is a peculiar membrane 
traversed by veins, and the irregularity of the sinuous lines, by 
which it is sometimes marked, are considered as strongly sup¬ 
porting this view ; such irregular figures being considered to be 
at variance with the notion of its being an adhesion of vesicles 
of cellular tissue: others, regarding it to be a form of cellular 
tissue, contend that the irregularity of the reticulations, or sup¬ 
posed lymphatic vessels, is nothing more than is observed in a 
section of any portion of cellular tissue. In answer to the 
argument, that on the removal of the cuticle the subjacent 
tissue dies, instead of becoming cuticle, it is maintained that 
this is no reason why itself should not have originally been 
composed of a cellular tissue ; and, as regards the non-formation 
of cuticle, by the change of the tissue immediately beneath the 
original covering, it is an axiom in physiology, that a part once 
fully formed is incapable of any subsequent change whilst in a 
living state; thus, a zone of wood never contracts or expands 
after it is deposited, though new matter may be added to any 
part. The arrangement of tissue, when it once becomes fixed, 
continues, therefore, unchangeable as long as it is maintained 
by the vital force. It may further be remarked, that separable 
cuticle may often be traced to that which is younger, and in¬ 
separable from the other cellular substance with which it is in 
contact, and from which it possesses no organic difference. 
The cuticle is generally perforated by small openings, and 
these are termed stomata, or pores ; by some they are regarded 
as imperforated glands, whilst others regard them as openings 
connected with respiration. They are composed, in some of 
the species of Crinum , of two elastic kidney-shaped bladders, 
which lie over an opening of the cuticle, and are pressed 
together by the action of two opposing springs, by whose con¬ 
traction the pores are opened. They are not found on mosses 
nor on fungi, on algae nor on lichens, on submerged plants 
nor on plants growing in darkness, on roots nor on the ribs of 
leaves ; they are frequently found on one surface of a leaf, but 
are absent from the other ; they may generally be seen on the 
VOL. v. NO. II. E 
