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The External Form of Plants. 109 
stronger plants. Accordingly as they belong to the stem as in 
the vine (Fig. 196), or to the leaf as in the tare, they are 
called stem- or leaf-tendrils. The same distinction is made_ 
between Jranch-spines as in the sloe (Fig. 197), and 4af-- 
spines as in the holly (Fig. 172, p. 98); ze. stiff and very 
sharp-pointed. structures arising from the transformation of a 
stem or leaf, or a part of one of these organs, and which are 
therefore not mere epidermal growths.! Prick/es, although 
Fic. 197. —Branch-spines of the sloe, Fic. 198.—Prickles of the rose. 
' Prunus spinosa. fe 
sharp-pointed like spines, are distinguished from them by 
belonging to the epidermis only, and therefore easily break- _ 
ing off smoothly, which is never the case with spines; a 
good illustration is furnished by the rose (Fig. 198; -se 
also p. 63). An important class of these subsidiary organs 
are fairs—delicate appendages of the epidermis which are 
1 [Tendrils and spines may also both be metamorphosed stipules ; the 
former is generally believed to be the morphological nature of the ten- 
drils in the Cucurbitaceze ; the latter is the case in the ‘acacia-tree,’ 
. Robinia (Fig. 184, p. 103). In Lathyrus Aphaca (Fig. 146, p. 92), 
the whole of the’leaf is converted into a tendril ; but more frequently > 
only the upper pinnee of a compound leaf, as in many Leguminosze, 
or the extended nnid- rib, as in Glorzosa.—ED. | 
