XIV, 
GLOSSARY. 
Tomentose: covered with soft cottony hairs. 
Transpiration Current : the ascending sap, as 
it is absorbed by the root hairs, passes 
thence through the roots, stem, and 
branches to the leaves, and from 
the leaves gives off part of its 
water through the stomata in invis¬ 
ible vapour. This upward flow of 
the sap takes place through the sapwood 
or alburnum, which is thus essential to 
the life and growth of an exogenous tree. 
The sap immediately under the bark is a 
descending flow of tissue food prepared 
in the laboratory of the leaves. 
Turbinate : broad at one end and narrow at the 
other like a top. 
Umbel: a cluster of flowers that all spring from 
the summit of a common peduncle. The 
flowers may be sessile or each may have 
its own stalklet or pedicel. A capitulum 
has the seed-vessels still more closely 
united. 
Veins: the more or less rigid (fibro-vascular) 
structures that, together with the petiole 
and midrib, form the framework of the 
leaf. This framework fulfils two main 
functions: 
(а) It spreads the leaf blade to the light 
and so facilitates the formation of 
food materials. 
(б) It provides channels for conveying 
the nutrient fluids to and from the 
leaf. 
Whorl: (pro. whurl): a circle of leaves or 
branches round a stem; or one of the 
circles in the organs of a flower. 
