DR. M. T. MASTERS ON THE PASSIFLORACEÆ. 595 
larger than the central one. Frequently the nerves project beyond the margin of the 
leaf in the form of a small mucro. | 
The variations in the colour of the leaf afford useful characters as well as add con- 
siderably to the beauty of the plant in special instances. The diversities in amount and 
quality of pubescence are of little value for specific purposes, though it may be inciden- 
tally remarked that stellate pubescence is very rare in the order, nor is it at all cus- 
tomary to meet with the very shaggy investment we sometimes find in other plants, 
though a covering of glandular hairs is characteristic of certain species, e. y. Passi- 
flora fetida. i 
Petiole.—The leaves of this order are usually stalked, the stalk itself generally present- 
ing one feature which, though not absolutely peculiar to the order, is nevertheless very 
characteristic of it—the presence of glands. These glands present sundry diversities: in 
some species they are sessile, in others they are stipitate, disposed with tolerable regu- 
larity or, in other instances, irregularly scattered; small in some species, in others they 
attain to considerable dimensions. That they are true glandular organs in some species 
is evident from their secretion and from their internal structure, while their morpho- 
logical nature is elucidated by a study of their development, and by various species of 
Tacsonia, in which the glands appear as so many miniature leaf-lobes emerging from 
either side of the petiole towards the upper surface. 
In some species the glands are represented by small thread-like processes, as in P. 
ligularis. The petiolar glands in their typical state are therefore laminar processes, 
strueturally adapted for the purpose of secretion. In other instances they do not appear 
to secrete and are then present in the form of small leaf-lobes or of thread-like processes. 
The study of their development shows not only that they are relatively larger in the 
juvenile stage, but that their functions are more actively carried on at that time than sub- 
sequently. "Too much stress must not be laid on their number or their position. Thus 
in P. edulis and other species the petiolar glands are at the very apex of the stalk in 
young leaves, while in adult ones they are nearly + of an inch below it. The number, 
too, is confessedly variable, even on the same plant. 
Stipules.—The existence of these organs is universal in the order. Varying much in 
size and external configuration, and to a less degree in internal structure, they often 
afford useful means of discrimination between one species and another. In some cases 
they are small linear threads, as insignificant in appearance as purposeless in action. 
In other cases they are large, and by their size and structure are enabled to fulfil the 
double purpose of protection to the young leaf and of respiration. In form they vary 
considerably in different species, and thus afford useful means of discrimination. What- 
ever form they assume, they are very generally more or less inequilateral, the obliquity 
resulting from the impeded development of that side of the stipule nearest to the stem, 
the larger portion of the stipule being always furthest away from the supporting axis. 
The venation of the stipules is either multicostate or unicostate ; in the former case the 
nerves always converge to the apex, in the latter instance the midrib frequently extends 
beyond the margin in the form of a mucro. In both the smaller veins break up into an 
intricate network. The difference in the venation points to a different morphological 
| 4 K 2 p 
