68 J. SAUNDERS—CLIMBING PLANTS OF THE SOUTH MIDLANDS. 
The extensive genera Vicia and Lathyrus usually possess branched 
tendrils which are modified midribs of leaves. An extreme case is 
presented by Lathyrus Aphaca , which is sporadic in cornfields, 
that species having its leaves reduced to tendrils, the office of the 
foliar organs being effected by an unusual development of the 
stipules. The leaflets are present on seedlings, but are rarely 
seen on mature plants. In the closely allied species Lathyrus 
Nissolia , the grass vetch, a very local plant of sandy soils, both 
tendrils and true leaves are suppressed, the latter organs being 
replaced by modified petioles which are developed into elongate, 
grass-like phyllodes. 
Hooks. —There are no British plants that climb by hooks which 
when irritated by contact increase in thickness. Exotic examples 
of these are furnished by TJncaria (Rubiacese), Olax (Olacinese), 
and Hugonia (Linacese), which are members of natural orders 
represented by plants that are native in this district. (Sach’s 
‘Text-book of Botany,’ 2nd ed., p. 962.) 
Prickles. — Another means of obtaining support from more 
strongly growing plants is attained by means of prickles. These 
are epidermal developments, and may be regarded as bundles of 
hardened hairs with pointed apices. Eamiliar examples are 
furnished by the brambles and wild roses, in which the prickles 
are spreading or point downwards. The latter feature is most 
frequent, especially in the dog-roses, strongly growing stems of 
which may frequently be seen rising several feet above the general 
level of country hedgerows. 
Minute prickles or climbing hairs occur on the six ridges of the 
stems of wild hop, and no doubt assist the plant in clinging to any 
available means of support. 
Climbing plants furnish subjects for outdoor observation at all 
periods of the year. In Spring and Summer the phenomena 
associated with growth amply repay the closest attention, and in 
mid-Winter a little discrimination enables one to distinguish the 
various genera of plants of which the stems are exposed in the 
leafless coppices and hedgerows. 
Addendum. 
The Vernal Shoots of Ivy. —The habits of these organs varies in 
accordance with their environment. Those which grow remote 
from means of support droop at various angles, while their apices 
are heliotropic over several internodes. Those which grow close to 
a support have their extreme tips alone heliotropic, the next older 
internodes being non-heliotropic owing to the climbing habit having 
overcome the heliotropic; the internodes near the apex are closely 
oppressed to the supporting medium, that position being maintained 
until the adventitious roots, by which the adhesion is rendered 
permanent, are developed. 
