SIZE OF LEAVES. BUDS PROM EDGES. 



159 



last plan, it would have been simply pinnate. If on the plan of 

 the lowest division, in which there is a complete series of 

 secondary leaflets on each side, the leaf would have been bi- 

 pinnate. And if the whole leaf had been constructed upon the 

 plan of the minutely-subdivided portion of the second division, 

 it would have been tri-pinnate. 



239. These are some of the most interesting varieties in the 

 form of leaves, depending upon the degree in which the paren- 

 chyma or cellular flesh is supplied, to fill up the interspaces 

 between the veins. Of those which depend upon the various 

 distribution of the veins themselves, it is not intended here to 

 speak ; since every plant furnishes materials for observation of 

 these differences. In regard to the size of leaves, it may here be 

 mentioned that, whilst in some species they are nearly micros- 

 copic, in others, especially of the Palm tribe, single leaves attain 

 the length of from 30 to 40 feet. 



240. There are some leaves possessed of the power of deve- 

 loping buds from their edges, a fact which will hereafter (Chap, 

 xii.) be shown to be important. One of these is the Bog-Orchis 

 (Malaxis paludosa) of English marshes; in which these buds 

 may be distinctly seen, though the whole plant is very small. A 

 better example, however, 



is the Bryophyllum caly- 

 cmum,whichisa species in- 

 habiting tropical climates, 

 and known as the air- 

 plant or leaf-plant, from, 

 the circumstance of a single 

 leaf, without either stem 

 or roots, being able to 

 maintain its life, and even 

 to grow and flower, whilst 

 hung up in a damp arid 



warm atmosphere, with- FlG< 68 ._ L KAF OF BRYOPHYLLUM CALYCINUM, 

 OUt the Contact of Soil to BEARING BUDS AT STB EDGES. 



any part of it. The little buds," which develope themselves at 

 the edges of the leaves, may become perfect plants, before sepa- 



