OUTLINES OF BOTANY. 
Xlll 
19. When the axis and its branches are slender and thread-like, the root 
is said to b e fibrous. — All plants produce fibrous roots,but especially annu- 
aU (@), in which the plant flowers and fruits the first season, and perishes, 
root and all, as soon as the process is completed. 
20. It frequently becomes distended and thickened, or fleshy, by the 
deposition of digested and organizable matter (in the form of starch , &c.) 
within its cells ; this deposit forming a stock for future growth, on which 
new stems or shoots, &,c., may feed, even when cut off from any external 
supply. 
21. Roots of this sort assume a variety of forms, such as the conical root, 
which tapers regularly downwards from the base or crown (the part which 
joins the stem) to the apex, as in the carrot; the spindle-shaped or fusi¬ 
form, which tapers upwards as well as downwards, as the radish ; and tur¬ 
nip-shaped or napiform , when the base is enlarged laterally so as to become 
much broader than long. These are particularly characteristic of bien¬ 
nials ((g)), which form such a root during their first year's growth, but do 
not flower until the second season, when they rapidly consume this stock, 
and die from exhaustion as soon as the process of flowering and fruiting is 
completed. In these cases the thickening takes place in the main trunk of 
the root, or tap-root. 
22. In perennial roots (1|), viz. those which survive .and produce flower¬ 
ing stems from year to year, as well as in those of many biennials, the ac¬ 
cumulation often occurs, partly in its branches, forming tuberous roots 
when they are irregularly knobby, or palmate roots when several thickened 
branches proceed from a thicker base, somewhat like a hand with the 
fingers spread ; or else wholly in a cluster of branches from a common base, 
forming fasciculated or clustered roots, as in the Dahlia, Paeony, and some 
Buttercups. 
23. *Roots not only spring from the root-end of the primary stem in ger 
mination, but also from any subsequent part of the stem under favorable 
circumstances, that is to say, in darkness and moisture, as when covered b> 
the soil or resting on its surface. 
24. They may even strike in the open air and light, as is seen in the 
copious aerial rootlets by which the Ivy, the Poison Ivy (p. 79), and the 
Trumpet Creeper (p. 2911, climb anc^adhere to the trunks of trees or other 
bodies ; and also in Epiphytes or Air-plants , of most warm regions, which 
have no connection whatever with the soil, but germinate and grow high in 
air on the trunks or branches of trees, &c.; as well as in some terrestrial 
plants, such as the Banian and Mangrove, that send off aerial roots from 
their trunks or branches, which finally reach the ground. 
25. In parasitic plants, the roots fix themselves to or penetrate the 
surface of other plants, and take their nourishment from them : some, like 
the Mistletoe (p. 398), attaching themselves to the wood of the trunk or 
branches of trees; others ( root-parasites ), like the Beech-drops and the 
Orobanchaceae (p. 289), to their roots under ground. 
4. The Stem. 
* Its External Modifications. 
26. The Stem is sometimes simple , that is unbranched, and continued 
upwards by its growing apex (or terminal bud) only ; but more commonly it 
becomes branched. All Phacnogamous Plants necessarily have a stem. In 
those which are termed acaulescent or stemless in botanical description, it is 
merely subterranean or very short. 
27. The Branches spring from lateral,' or axillary buds; which are 
new growing pointsappearing (usually singly) in the axils of the leaves, 
i. e. in the angle formed by the leaf or its stalk and the stem on the upper 
