ORGANS OF NTJTfilTION. 



Fig. 276. 



143 



Fig. 275. 



Fig. 277. 



Fig. 279. Fig. 280. Fig. 281. 



Fig. 275. Transverse section of a bud to show the leaves arranged in a 



valvate manner. 

 Fig. 276. Transverse section of a Inid to show Imbricate vernation. 

 Fig. 277. Transverse section of a bud to show twisted or spiral vernation. 

 Fig. 278. Transverse section of a t)ud to show induplicate vernation. 

 Fig. 279. Transverse section of a bud showing equitant vernation. 

 Fig. 280. Transverse section of a bud showing ol>volute vernation. 

 Fig. 281. Transverse section of a bud showing supervolute vernation. 



the Sage {fig. 280), the vernation is haJf-equitant or ohvohite ; 

 and 4th, when a convolute leaf encloses another which is rolled 

 up in a like manner, as in the Apricot, the vernation is supper- 

 volute {fig. 281). 



The terms thus used in describing the different modes of ver- 

 nation are also applied in like manner to the component parts 

 of the flower-bud, under the collective name of cBstivation or 

 •prcefioration. We shall have therefore to refer to them again, 

 together with some others, not found in the leaf-bud, when 

 speaking of the flower-bud. 



4. LAMINA OE BLADE. 



"We have abeady seen that the leaf {figs. 247 and 248) in its 

 most highly developed state consists of three parts ; namely, of 

 a lamina or blade ; a -petiole or stallc ; and of a stipular or vaginal 

 portion. We have now to describe each of these portions, com- 

 mencing with the lamina or blade. 



Venation. — The term venation is applied generally to indicate 

 the various modes in which the veins are distributed throughout 

 the lamina. These veins have also been called Nerves, and their 

 distribution Nervation; but the latter terms, by indicating an 

 analogy which does not exist between them and the nerves of 

 animals, are better avoided ; hence we shall in future always use 

 the terms veins and venation. 



