THE DESCRIPTION OF A LEAF. 



I. THE KIND. 



Simple : When the blade is in one piece. (See pp. 18 to 36.) 

 Compound : When the blade is divided into smaller parts, called 

 leaflets. A compound leaf may resemble a twig with 

 simple leaves, but the former never has buds growing from 

 it, never leaflets regularly alternate, and always a leaflet at 

 the end, in our species. Notice also that leaflets grow only 

 from opposite sides of the central stalk, and so lie in one 

 plane, while simple leaves often grow on all sides of the 

 central twig. (See pp. 14 and 16.) 



Pinnate: When the leaflets are placed along a central stalk. 

 (See p. 16.) 



Palmate : When the leaflets are placed around a centre. (See p. 

 U 20a, 26d, 26f.) 



Figures placed before these words, as 5-9-pinnate or 5-pal- 

 mate, refer to the number of leaflets. 



II. THE ARRANGEMENT. 



Alternate : Growing one by one and each higher on the stem than 



the last. (See pp. 16, 22, 24, 34.) 

 Opposite : Growing in pairs on opposite sides of branch and at 



equal height upon it. (See pp. 18, 14 la, 22a, 36a.) 

 Alternate pairs : Leaves that are really alternate sometimes are so 



near together as to appear opposite on very short side twigs, 



while the true arrangement is seen on the newer wood of 



the young shoots. This peculiarity is very noticeable in 



the Birches. (See p. 30 68b, 68d.) 

 Whorled : In circles of three or more around a branch or stem. 



(See p. 36 84a.) 

 Two-rowed : Growing in two rows on opposite sides of twigs, as in 



the Elms. (See p. 36 80a, Sla.) 



Solitary : One by one, not grouped. (See p. 36 79a, 81a.) 

 Shingled : With small flat leaves overlapping closely like shingles. 



(See p, 36 83a, 84c.) 

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