36 CLASS-BOOK OF BOTANY. 
Flowers which are entomophilous,* or insect-fertilised, 
are characterized by their being— 
a. Conspicuous either individually or by aggregation ; 
b. By bright colours ; 
c. By the production of nectar or scent; 
d. By the stamens and stigmas being relatively small, 
and usually included within the floral envelopes (not 
_ exserted); and, lastly, 
e. By the quantity of pollen produced being comparatively 
small, and its consistence more or less granular or 
waxy, but not dusty. 
8. SwEET Pea (Lathyrus odvratus). 
We now come to the examination of a type which we shall 
find to be very common, and very constant in its characters. 
This plant is a climbing herb, but it climbs in a manner 
different from Clematis—viz., by means of organs specially de- 
veloped for the purpose, which are termed tendrils. A glance 
at the leaf will show what these organs are in this case. 
The leaf is alternate 
> and pinnate, and pro- 
{) vided with small sti- 
pules at the base; 
ae jo. but the lower pair of 
( RO leaflets are alone de- 
C 4. ~ veloped, all the rest 
") being reduced to mid- 
ribs and acting as the 
climbing organs. It 
has been demon- 
strated (by Darwin 
and others) that these 
tendrils are not only 
sensitive to a slight 
irritation or to gentle pressure, curving in the direction of the 
touching body, but that they also perform a regular revolving 
moyeinent, so that by one or other means they are brought 
into contact with objects on which they climb. . 
The stems and the rachis of the leaves are more or less 
broadly winged, the wings evidently performing some of the 
leaf-functions to make up for the loss of these in great part by 
the leaves themselves. The flowers are produced singly, or in 
twos or threes, on long peduncles which spring from the axils 
of the leaves. Note the 5-lobed inferior calyx, and the 6 irre- 
gular petals attached to the base of the calyx-tube (perigynous). 
eae SE a es 
Fig, 40. Leaf of Sweet Pea, with tendrils 
(reduced), 
* Gr. entoma, insects; philos, loved, 
