194 APPLIED BIOLOGY 



185. Floral Leaves. Careful study of the development 

 of flowers has led botanists to regard the sepals, petals, 

 stamens, and pistil as highly modified leaf-like structures 

 ( 202), and they are sometimes called floral leaves. 



186. Forms of Leaves. Students who have not become 

 acquainted with the various common forms of leaves should 

 compare them whenever an opportunity offers. Special 

 names are applied to the shapes of leaves and to the different 

 kinds of notched and lobed margins. For these names con- 

 sult the glossaries of books for identifying plants, and the 

 figures in such books as Gray's " Lessons with Plants." 

 Such names are not worth memorizing unless one makes 

 frequent use of manuals for identifying plants. 



187. Veins of Leaves. The type of veining found in 

 the bean leaf is known as netted veining, while that seen in 

 the corn plant is parallel veining. Most monocotyledons 

 have parallel veining, and most netted-veined leaves are 

 found on dicotyledons. The arrangement of the veins in 

 these two types appears to have nothing to do with the work 

 of the leaves, for the two kinds of leaves perform essentially 

 the same functions. The kind of veining is chiefly of interest 

 in classifying plants, for it at once suggests either mono- 

 cotyledons or dicotyledons; and this suggestion can be 

 tested by examining the structure of the stem ( 161) and 

 certain points with regard to the flowers ( 197). 



188. Simple and Compound Leaves. The bean leaf has 

 been described as compound because its blade is divided into 

 separate parts or leaflets. For convenience in identifying 

 and describing plants, botanists have termed those com- 

 pound leaves with leaflets arranged on sides of the leaf- 

 stalk (Fig. 58), as in honey-locust, black locust, elder, 

 ash, pea, parsnip, etc., pinnate (meaning, arranged like a 

 feather) ; while the term palmate (meaning, like a hand) is 

 applied to those leaves like clover, horse-chestnut, buck- 

 eye, in which the leaflets are all attached to the end of 



