10 



EXPLANATION OF TERMS 



sides of a common stalk, or rachis. In palmately compound leaves 

 they all spring from the summit of the common petiole, like the 

 fingers of a hand. In a bi-pinnate leaf the leaflets are again 

 divided to the base, as in the fronds of many ferns. 



The terms used in describing the shapes and margins of leaves 

 may be best understood by a study of the figures (adapted from 

 Gray's Structural Botany) and of the definitions in the glossary 

 at the end of the book. 



Leaves are sometimes broader at apex than at base, in which 

 case the prefix ob, meaning inversely or oppositely, is often con- 

 venient. 



2 3 4 5 6 



Leaf-margins, Lobed Leaves, and Venation. — 1. An entire leaf. 2. A 

 toothed or dentate leaf. 3. A lobed leaf, the divisions extending not more 

 than half way to the midrib. 4. A parted leaf, the divisions reaching nearly 

 to the midrib. 5. A parallel-veined leaf. 6. A net-veined leaf. 



The Flower. 



The flower comprises all of the plant parts which have to do 

 with reproduction, that is, with the formation of fertile seeds. 

 Some plants, however, reproduce without the aid of true flowers 

 and do not set seed. Such are the so-called "flowerless plants" 

 (Cryptogams), of which only the ferns are here described. 

 Flowering plants, or seed plants, are known as Phaenogams. 



The parts of a flower (any one of which may be wanting in 

 some cases) are as follows: 



The perianth comprises both calyx and corolla, or only the 

 calyx when the corolla is wanting. The showy part of most 

 Irises, Lilies, Eriogonums, etc., is the perianth. 



The calyx forms usually an outer circle of greenish parts, 

 mostly for purposes of protection. It may be of distinct sepals, 

 or these may be united into a cup-shaped, bell-shaped, or some 

 other form of one-piece calyx. 



The corolla forms an inner circle of parts usually colored for 

 purposes of attraction, since flowers depend largely upon insects 

 for the carrying of their pollen. It may be either choripetalous, 

 that is, composed of separate parts (petals) as in the Buttercup, 

 Mustard, Rose, etc. ; or the corolla may be sympetalous, that is, 



