FREQUENCY OF SEEDING 



113 



The first class includes all annuals and biennials, and 

 those perennials, native and foreign, which flower after 

 several seasons' growth and then perish. All these are, 

 biologically, annuals. The most remarkable mono- 

 carpic perennial is the American aloe, Agave americana. 

 This wonderful plant grows very slowly, forming a 

 gigantic rosette of long, thick, fleshy leaves, two or three 

 each year. At last it flowers, bearing a huge inflorescence, 



a 



FIG. 33. FALSE-OAT GRASS (Arrhenatherum avenaceum). (REDUCED.) 



a, erect flowering shoot ; b, decayed leaf-bases ; c, swollen internode ; 

 d, lateral branch ; e, horizontal part of rhizome ; /, axillary bud. 



reaching in some cases a height of 20 feet. It lives to 

 a great age before flowering, sometimes a hundred years. 

 But the act of flowering and fruiting is so exhausting that 

 the plant is unable to survive it, and it dies. This aloe is 

 therefore, in spite of its longevity, biologically, an annual, 

 for, like all annuals, it seeds once and dies. 



To the polycarpic group are assigned all trees and 

 shrubs, herbaceous perennials, and geophytes. 



