32 MORPHOLOGY, OB COMPAEATIYE ANATOMY. 



Herbaceous steins, or such as do not become woody, but die 

 down to the ground in winter, are produced by annual and biennial 

 plants, and in each successive flowering axis of herbaceous peren- 

 nials ; to these also are analogous the yearling shoots of arbores- 

 cent plants. Taken by themselves, they are either annual or 

 biennial ; that is to say, they bear on the same axis green leaves 

 belonging either only to one or to two seasons of growth. Annual 

 herbaceous stems alone, of course, occur on true annual plants : 

 they are produced also by those perennial herbaceous plants which 

 send up a flowering stem from beneath the soil in spring ; and 

 with these are to be included most plants forming bulbs and 

 corms. 



In ordinary annuals the plumule or terminal bud of the seed shoots up 

 at once into a more or less branched flowering stem, and the entire plant 

 dies away after the seeds are perfected in autumn. Examples of this 

 form may be seen in the Sweet Pea, Veronica hederafolia (fig. 13), &c. 

 In many perennial herbaceous plants forming rhizomes, and in most 

 bulbous plants, a subterraneous bud shoots up in the early part of each 

 season of growth, bearing green leaves and forming* a flowering stem 

 (fig. 23, b) ; in the autumn the whole of these structures disappear (c, rf), 

 while resting buds () are formed in the axils of the lower leaves beneath 

 the soil, to repeat the growth in the following season. We have examples 

 of this kind of stem in the Solomon's Seal, Garden Pseony, Aconite, 

 Asparagus, &c. The young fleshy shoot with rudimentary leaves which 

 these plants form in early spring is sometimes called a turio (this is ex- 

 emplified in the edible part of the Asparagus). The leafy flowering 

 steins of bulbs and tubers, such as those of the Lily, Potato, Orchis, &c., 

 furnish further examples of the annual herbaceous stem. 



Biennial herbaceous stems are found in true biennials and many 

 herbaceous perennials. They are distinguished by the lower part 

 of the axis producing green leaves in one season, and the upper 

 portion growing into a flowering stem in the following year. 

 Generally speaking, the internodes are little developed in the 

 growth of the first season, and the leaves are often larger as well 

 as more crowded ; they also frequently die away early in the second 

 season. 



Examples of the biennial herbaceous stem are o be found in such 

 true biennial plants as the Turnip, the Thistle, Parsley, c. Here, when 

 the seed is sown, it produces a stem with scarcely developed internodes, 

 supporting a number of leaves which form a kind of tuft or rosette upon 

 the ground ; this growth remains almost at rest during the winter, and 

 in the succeeding spring the terminal bud shoots up into a flowering- 

 stem. Sometimes several axillary buds also grow up into flowering stems, 

 giving rise to the condition called "radix mutticeps:" this may occur 

 either in biennials or perennials. A similar kind of stem is found in 

 such perennial herbaceous plants as the common Daisy, the Dandelion, &c., 



