BOTANICAL INTRODUCTION 47 



of this classification is to enable the investigator to identify 

 with certainty the specimen under investigation. In some 

 cases this can be done only after an elaborate study of the 

 plant ; but in the majority of instances, half-an-hour's v\^ork or 

 less should be sufficient to enable the student to name it. To 

 assist him in his work a key is here provided (v. p. 49). 



The Angiosperms are first sub-divided into two sub-classes, 

 the Dicotijledons and Monocotyledons. The dicotyledons, on 

 germination, produce two seed-leaves or cotyledons, the mono- 

 cotyledons only one. The seed-leaves of the dicotyledons are 

 generally entire, simple, rather fleshy leaves, unlike those 

 subsequently produced by the plant. The solitary seed-leaf of 

 the monocotyledons is usually long, narrow and similar to 

 those subsequently produced. There are many other external 

 differences between the two classes. In the monocotyledons, the 

 chief veins of the leaves run more or less parallel to the length 

 of the blade ; in the dicotyledons the chief veins are not 

 parallel to each other, and are connected by a net-work of 

 smaller veinlets. Leaves of the former kind are said to be 

 parallel- veined. The latter are termed reticulate, or netted- 

 veined leaves. The parts of the flowers in a monocotyledon 

 are usually in three, or in some multiple of three. In the 

 dicotyledons there are usually /b?r?" or five, or some multiple of 

 either of these numbers. The monocotyledon produces a root 

 consisting of a number of fibres, which sprout from the base of 

 the young plant. The seedling dicotyledon produces a single 

 root (tap-root), which is continuous with the stem. These 

 differences may be tabulated thus : — 



Monocotyledons. Dicotyledons. 



1. One seed-leaf. Two seed-leaves. 



2. Fibrous roots. Tap-root. 



3. Parallel- venation. Netted- venation. 



4. Parts of flower in threes. Parts of flower in fours 



or fives. 



