10 OKGANOGRAPHY AND GLOSSOLOGY. 



the neck or crown of the root. A root is fibrous (r. fibrosa) when its fibrils 

 form a bundle of fine, long, scarcely-branched threads (Meadow-grass, fig. 23) ; 

 nodose (r. nodosa), when the fibres are swollen at intervals (Dropioort, fig. 26)'; 

 tuberous (r. tuberosa), when the fibres are much swollen in the middle, thus 

 becoming stores of nourishment destined to sustain the plant (Dahlia, fig. 27). 

 The Orchis root (fig. 28) is both fibrous and tuberous, the ovoid or palmate 

 tubers being reservoirs of nutritious matters, and the cyliudrie fibres being organs of 

 absorption. The fibres of young Crocus roots are similarly swollen. 



We have said that the stem has the power of emitting adventitious roots ; these 

 are sometimes artificially induced (as on slips or layers), sometimes spontaneously 

 developed on the nodes of the stem : when these emerge at a considerable height, 

 and descend to enter the earth, they are termed aerial roots (many tropical climbers 

 and epiphytal orchids) ; when they spring from the lower branches of creeping 

 plants, they are called accessory roots (Strawberry, Ground-ivy). 



THE STEM. 



The stem (caul is) is that portion of the vegetable axis which grows in an opposite 

 direction to the root. It branches by means of shoots, which originate in the 

 axils of the leaves. The stem exists in all phaxiogams, but is sometimes scarcely 



developed, when the 

 leaves and flowering 



plant is termed stemlcxs 

 (p. acaulis), and its leaves 

 radical (f.radicalia, Hya- 

 cinth, Dandelion, fig. 29). 

 The stem is perennial (c. 

 perennis) when it livi-s 

 many years (Strawberry) ; 

 annual (r.. annuus), when 

 it only lives one (Wheat) ; 

 biennial (c. biennis), when 

 it lives two years (Carrot) ; 

 a biennial stem usually 

 produces leaves only the 

 first year, and in the 

 second it flowers, fruits, and dies. The stem is herbaceous (c. herbaceus) when soft 

 and easily broken; such are annual, biennial, and many perennial stems; it is 

 woody (c. lignosus, fruticosus) when it forms a solid, more or less durable wood 

 (Oak) ; it is su/ruticose (c. su/ruticosus) when the lower part is hard, and remains 

 above ground for many years, while the branches and twigs die, and are annually 

 renewed (Rue, Thyme, Sage, Bitter-sweet). The woody stem of trees is called a trunk. 





