Ouar. 1. STRUCTURE OF THE LEAVES. 5 
outwards, with their pedicels of a purple colour. Those on the 
extreme margin project in the same plane with the leaf, or more 
commonly (see fig. 2) are considerably reflexed. A few tentacles 
spring from the base of the footstalk or petiole, and these are 
the longest of all, being sometimes nearly 4 of an inch in length. 
On a leaf bearing altogether 252 tentacles, the short ones on 
the disc, having green pedicels, were in number to the longer 
submarginal and marginal tentacles, having purple pedicels, as 
nine to sixteen. 
A tentacle consists of a thin, straight, hair-like pedicel, carry- 
ing a gland on the summit. The pedicel is somewhat flattened, 
and is formed of several rows of elongated cells, filled with purple 
fluid or granular matter.* - There is, however, a narrow zone 
close beneath the glands of the longer tentacles, and a broader 
zone near their bases, of a green tint. Spiral vessels, accom- 
panied by simple vascular tissue, branch off from the vascular 
bundles in the blade of the leaf, and run up all the tentacles 
into the glands. 
Several eminent physiologists have discussed the homological 
nature of these appendages or tentacles, that is, whether they 
ought to be considered as hairs (trichomes) or prolongations of 
the leaf. Nitschke has shown that they include all the elements 
proper to the blade of a leaf; and the fact of their including 
vascular tissue was formerly thought to prove that they were 
prolongations of the leaf, but it is now known that vessels some- 
times enter true hairs.t| The power of movement which they 
possess is a strong argument against their being viewed as hairs. 
The conclusion which seems to me the most probable will be 
given in Chap. XV., namely that they existed primordially as 
glandular hairs, or mere epidermic formations, and that their 
upper part should still be so considered; but that their lower 
* According to Nitschke (‘ Bot. 
Zeitung,’ 1861, p. 224) the purple 
fluid results from the metamor- 
phosis of chlorophyll. Mr. Sorby 
examined the colouring matter 
with the spectroscope, and in- 
forms me that it consists of the 
commonest species of erythro- 
phyll, “ which is often met with in 
leaves with low vitality, and in 
parts, like the petioles, which 
earry on leaf-functions in a very 
imperfect manner. All that can 
be said, therefore, is that the hairs 
(or tentacles) are coloured like 
parts of a leaf which do not fulfil 
their proper office.” 
+ Dr. Nitschke has discussed 
this subject in ‘Bot. Zeitung,’ 
1861, p. 241, &e. See also Dr. 
Warming (‘Sur la Différence entre 
les Trichomes,’ &c., 1873), who 
gives references to various publi- 
cations. See also Groonland and 
Trécul, ‘ Annal. des Se. nat. bot.’ 
(4th series), tom. iii. 1855, pp. 
297 and 303. 
