38 STEMS. [SECTION 6. 



only a part of the year. They are of course herbs ; they spring from the 

 seed, blossom, mature their fruit and seed, and then die, root and all. An- 

 nuals of our temperate climates with severe winters start from the seed in 

 spring, and perish at or before autumn. Where the winter is a moist and 

 growing season and the sumaier is dry, winter annuals prevail; their seeds 

 germinate under autumn or winter rains, grow more or less during winter, 

 blossom, fructify, and perish in the following spring or summer. Annuals 

 are fibrous-rooted. 



85. Biennials, of which the Turnip, Beet, and Carrot are familiar ex- 

 amples, grow the first season without blossoming, usually thicken their 

 roots, laying up in them a stock of nourishment, are quiescent during the 

 winter, bnt shoot vigorously, blossom, and seed the next spring or summer, 

 maiuly at the expense of the food stored up, and then die completely. 

 Annuals and biennials flower only once ; hence they have been called 

 Monocarpic (that is, once-fruiting) plants. 



86. Perennials live and blossom year after year. A perennial herb, in 

 a temperate or cooler climate, usually dies down to the ground at the end 

 of the season's growth. But subterranean portions of stem, charged with 

 buds, survive to renew the development. Shrubs and trees are of course 

 perennial ; even the stems and branches above ground live on and grow 

 year after year. 



87. There are all gradations between annuals and biennials, and between 

 these and perennials, as also between herbs and shrubs ; and the distinc- 

 tion between shrubs and trees is quite arbitrary. There are perennial herbs 

 and even shrubs of warm climates which are annuals when raised in a cli- 

 mate which has a wiuter, — being destroyed by frost. The Castor-oil plant 

 is an example. There are peremiial herbs of which only small portions 

 survive, as off-shoots, or, in the Potato, as tubers, etc. 



Section VI. STEMS. 



88. The Stem is the axis of the plant, the part which bears all the 

 other organs. Branches are secondary stems, that is, stems growing out of 

 stems. The stem at the very beginning produces roots, in most plants a 

 single root from the base of the embryo-stem, or caulicle. As this root 

 becomes a descending axis, so the stem, which grows in the opposite direc- 

 tion is called the ascending axis. Rising out of the soil, the stem bears 

 leaves ; and leaf-bearing is the particular characteristic of the stem. But 

 there are forms of stems tliat remain underground, or make a part of their 

 growth there. These do not bear leaves, in the common sense ; yet they 

 bear rudiments of leaves, or what answers to leaves, although not in the 

 form of foliage. The so-called stemless or acaulescent plants are those 

 which bear no obvious stem icaulis) above ground, but only flower-stalks, 

 and the like. 



