TRANSFORMATIONS OF THE LEAF. 63 



295. In texture leaves may be membranous, or coriaceous (leathery), 

 or succulent (fleshy), or searious (dry), rugous (wrinkled), &c, which 

 terms need only to be mentioned. 



296. In the quality of surface, the leaf may be glabrous (smooth), 

 destitute of all hairs, bristles, &c, or scabrous (rough), with minute, 

 hard points, hardly visible. 



297. A dense coat of hairs will render the leaf pubescent when 

 the hairs are soft and short ; villous when they arc rather long and 

 weak ; sericeous, or silky, when close and satin-like ; such a coat may 

 also be lanuginous, woolly ; tomentous, matted like felt ; or Jloccose, in 

 soft, fleecy tufts. 



298. Thinly scattered hairs render the surface hirsute when they 

 are long ; pilous when short and soft ; hispid when short and stiff. The 

 surface will be 



- 299. Setous, when beset with bristly hairs called setae ; and spinous 

 when beset with spines, as in the thistle and horse-nettle. Leaves may 

 also be armed with stinging hairs which are sharp and tubular, con- 

 taining a poisonous fluid, as in nettles and Jatropha stimulans. 



300. A pruinous surface is covered with a bluish-white waxy pow T - 

 der, called bloom, as in the cabbage, and a punctate leaf is dotted with 

 colored points or pellucid glands. 



• 301. Double terms. The modifications of leaves are almost endless. Many 

 other terms are defined in the glossary, yet it will be found often necessary in the 

 exact description of a plant to combine two or more of the terms defined im order 

 to express some intermediate figure or quality ; thus ovate-lanceolate, signifying a 

 form between ovate and lanceolate, etc. 



302. Sub. The Latin preposition sub (under) prefixed to a descriptive term de- 

 notes the quality which the term expresses, in a lower degree, as subsessile, nearly 

 sessile, subserrate, somewhat serrate. 



CHAPTER VIII. 



TRANSFORMATIONS OF THE LEAF. 



Hitherto wo have considered the leaf as foliage merely — constituted the fit organ 

 of aeration by its large expansion of surface. This is indeed the chief, but not the 

 only aspect in which it is to be viewed. 



, 303. The leaf is a typical form, that is, the type or idea from which 

 the Divine Architect derived the form of every other appendage of the 

 plant. To trace out this idea in all the disguises under which it lurks 

 is one of the first aims of the botanist. Several of these foims of dis- 

 guise have already been noticad, e. g. 



