14 ODDER AND PASTURE PLANTS. 



(Fig. 5, St.) acts differently in different plants. In beans it grows 

 in length and lifts the cotyledons (Fig. 5, Cot.), which gradually 

 become flat and thin, above the ground. In peas it is short, and the 

 cotyledons remain hidden in the soil for a long time, enclosed within 

 the seed coat. 



Root system: Leguminous plants are annual, biennial or per- 

 ennial. When annual, like Crimson Clover, or biennial, like Sweet 

 Clover, the primary root of the embryo always develops into a tap- 

 root. When they are perennial, a taproot may be found, or the under- 

 ground system may consist of a rootstock, from which secondary 

 roots are developed. With a rootstock the system is generally 

 shallow and the plants depend on the surface soil for their food. A 

 taproot usually penetrates to a considerable depth and the plant 

 gets much of its food from the subsoil. Both secondary roots and 

 taproots are characterized by small tubercles or clusters of nodules. 

 The significance of these is discussed on page 18. 



Stems: The stems of leguminous plants are erect or ascending 

 as a rule. Only in a few cases, as in White Clover, are they creeping 

 and able to develop secondary roots from their joints. Plants of 

 this type form more or less spreading mats, in which individuals are 

 difficult to recognize. The same is often the case when the stems, 

 as in Flat Pea, develop from a spreading and extensively branched 

 rootstock. In some species and genera, as in Flat Pea and Vetches, 

 the stems are weak and are kept from falling to the ground by special 

 organs on the leaves, called tendrils (see below). 



Leaves: The leaves of leguminous plants are compound; that 

 is, each leaf consists of a number of leaflets each completely separated 

 from the others. The type a leaf consisting of a number of pairs 

 of leaflets and ending with an odd one is that of Sainfoin (Plate 23). 

 All other kinds are mere modifications of this type. Thus, when the 

 leaflets are only three, as in Red Clover, Alfalfa, Sweet Clover and 

 others, the well-known trifoliate leaf is obtained. In other species, 

 such as the vetches (Plates 24 and 25) and Flat Pea, the blades of 

 the upper leaflets are not developed ; only their ribs remain and they 

 are transformed into tendrils, the function of which is to support the 

 weak stems. 



Everybody knows that the plants in a field of peas or vetches 

 are sometimes so firmly tied together, when the stand is dense, that 

 to pull those at the end of a long row will move the plants at the other 

 end. This is because the tendrils wind about the stems and branches 

 of neighbouring plants and bind them together. These tendrils are 



