72 LEAVES. , 



Leaves considered with regard to the manner in which they sue- 

 ceed each other in different stages of the plant. 



1. Seminal, leaves which come up with the plant when it 

 first appears above the surface of the earth : as in the garden 

 bean ; tnese leaves are only the cotyledons or lobes of the seed, 

 which, after nourishing the young plant, decay. 



2. Primordial, leaves 'growing immediately after the semi- 

 nal leaves, and resembling them in position, form, and size. 

 The primordial leaf, according to the fanciful idea of a French 

 botanist, is a sketch which nature makes before the perfection 

 of her work. 



3. Characteristic, leaves which are found in the mature state 

 of the plant ; or according to the idea above advanced, nature 

 in them, perfects her design. 



It is not always, however, that this process with regard to 

 change of leaves takes place ; as in many cases the proper, or 

 characteristic leaf, is the only one which appears. 



There are many terms to express the mode o}' insertion of the 

 leaf; such as radical growing from the root (radix), cauline 

 growing from the stem (caulis), &c. 



To express imposition of leaves we find the terms, apposite, 

 alternate, &c. 



The form of the leaf is expressed by various terms, borrow- 

 ed from the names of different objects ; as digetate (from digitus, 

 the finger), &c. For the explanation of these different techni- 

 cal terms we must advise you to consult the vocabulary as of- 

 ten as you find those you do not understand. We will, how- 

 ever, illustrate some of the most common forms of simple* 

 leaves. 



Fig. 30. 



Orbicular, or the round leaf; the Nasturtion (Tropoeolum), 

 affords an example of this kind (See Fig. 30, a) ; this is also 



leaves with respect to succession Insertion of leaves Position Form 

 Orbicular. 



