OF PLANTS. 91 



shapes of the so-called living existences ; but there is yet 

 another condition, though truly, compared to that just 

 mentioned, one of very little importance, whereby the 

 examination of organic bodies is involved in difficulty and 

 complexity, to which human powers of comprehension are 

 not nearly equal with the assistance at present at their 

 command, 



By shape is understood the limitation of bodies in space ; 

 the limits or boundaries by which the definite shape is 

 separated from boundless space, are surfaces. Surfaces 

 themselves are either plane, and these again bounded by 

 lines, or curved, and then defined in different ways by the 

 relation of their parts to one or more lines. The plane 

 surfaces are easily constructed and arranged if their 

 boundary lines are straight, as also are the bodies 

 bounded by plane surfaces, like crystals. In planes 

 which are bounded by curves, the difficulty gradually 

 increases to that great complexity which the theory of 

 curved lines presents. On the other hand, only a few of 

 the curved surfaces, such as the sphere, the ellipsoid and 

 so on, are capable of accurate geometrical definition, the 

 conditions soon become so complex that they bid defiance 

 to the most acute combinations of the greatest mathema- 

 ticians. Now, all lines and surfaces which occur in 

 organized bodies, are curved, and almost always so 

 irregularly, that a geometrical definition of them is at 

 present out of the question. Thus, leaving out of view 

 all the other difficulties, we are already disabled from 

 using accurately defined geometrical terms, even in the 

 mere description of the particular organic forms, and we 

 are compelled to have recourse to comparisons, and a 

 peculiar technical language derived from them, which, 

 from the nature of its origin, is very ambiguous. Even 



