PLANT LIFE. 



39 



On the other hand in many plants lateral roots be- 

 come of more importance than the tap root, and this 



dies early. Plants of the latter kind 



are perhaps usually less deeply 

 rooted and therefore more easily 

 transplanted than those with a tap 

 root. In addition to the functions 

 mentioned above many roots serve 

 as special organs for storing food. 

 Examples are sweet potatoes, cas- 

 sava (tapioca or manioc plant), 

 carrot, beet, etc. 



The Leaves are the factories for 

 the production of the plant's food. 

 In some plants, as for example 

 most cacti, there are no leaves and 

 their function is assumed by the 

 green stem which may be flattened 

 to resemble a leaf somewhat. Some 

 plants hold their leaves only during 

 the growing season and are called 

 deciduous, while others retain them 

 at least until the next season's leaves have appeared, 

 often for several years, and are called evergreen. In 

 the temperate zones it is mostly the needle-leaved trees 

 (pines, spruces, cedars, etc.), that are evergreen, while 

 most of the broad-leaved trees, except a few like holly 

 and live oak, are deciduous. 



Parts of the Leaf. Leaves consist usually of a flat- 

 tened blade strengthened by the so-called nerves or 

 veins which also carry water to all parts of the leaf, 

 and of a stalk, called the petiole. Often there are two 

 little more or less leaf-like bodies attached at the base 

 of the petiole, called stipules. A complete leaf is 

 therefore said to consist of blade, petiole and stipules, 

 but many leaves may lack one or both of the last two. 

 The blade may be in one piece or may be lobed or di- 

 vided into several parts called leaflets, as for example 

 the three leaflets of a clover or oxalic leaf, or the 



BEET ROOT. 



