XXXVlll OUTLINES OF BOTANY. 



169. Tendrils (cirrki) are usually abortive petioles, or abortive pe- 

 duncles, or sometimes abortive ends of branches. They are simple or more 

 or less branched, flexible, and coil more or less firmly round any objects 

 within their reach, in order to support the plant to which they belong. 

 Hooks are similar holdfasts, but of a firmer consistence, not branched, and 

 less coiled. 



170. Thorns and Prickles have been fancifully called the weapons of 

 plants. A Thorn or Spine is the strongly pointed extremity of a branch, 

 or abortive petiole, or abortive peduncle. A Prickle is a sharply pointed 

 excrescence from the epidermis, and is usually produced on a branch, on 

 the petiole or veins of a leaf, or on a peduncle, or even on the calyx or 

 corolla. When the teeth of a leaf or the stipules are pungent, they are 

 also called prickles, not thorns. A plant is spinuus if it has thorns, aculeate 

 if it has prickles. 



171. Hairs, in the general sense, or the indumentum (or clothing) of a 

 plant, include all those productions of the epidermis which have, by a more 

 or less appropriate comparison, been termed bristles, hairs, down, cotton, or 

 wool. 



172. Hairs are often branched. They are said to be attached by the 

 centre, if parted from the base, and the forks spread along the surface in 

 opposite directions ; plumose if the branches are arranged along a common 

 axis, as in a feather ; stellate, if several branches radiate horizontally. 

 These stellate hairs have sometimes their rays connected together at the 

 base, forming little flat circular disks attached by the centre, and are then 

 called scales, and the surface is said to be scaly or lepidote. 



173. The Epidermis, or outer skin, of an organ, as to its surface and in, 

 dumentum, is 



smooth, when without any protuberance whatever. 



glabrous, when without hairs of any kind. 



striate, when marked with parallel longitudinal lines, either slightly 

 raised or merely discoloured. 



furrowed (sulcate) or ribbed (costate') when the parallel lines are more 

 distinctly raised. 



rugose, when wrinkled or marked with irregular raised or depressed 

 lines. 



umbilicate, when marked with a small round depression. 



umbonate, when bearing a small boss like that of a shield. 



viscous, viscid, or glutinous, when covered with a sticky or clammy 

 exudation. 



scabrous, when rough to the touch. 



tuberculate or warted, when covered with small, obtuse, wart-like pro- 

 tuberances. 



muricate, when the protuberances are more raised and pointed but yet 

 short and level. 



echinate, when the protuberances are longer and sharper, almost 

 prickly. 



setose or bristly, when bearing very stiff erect straight hairs. 



glandular-setose, when the setae or bristles terminate in a minute 

 resinous head or drop. In some works, especially in the case of Rose* 

 and Rubus, the meaning of setts has been restricted to such as are glan- 

 dular. 



glochidiate, when the setae are hooked at the top. 



