514 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



entering each of the two leaves. Then a zone or girdle will be also 

 noticed passing from one leaf to the other, outside the stem-cylinder. 



This is called the stipular zone or arcs. It is from this that the cords 

 are supplied to the leaf-like stipules. As this zone can supply any num- 

 ber of cords, so the number of stipules is often increased. 



If leaves arise singly from the stem — i.e. are "alternate" — then as a 

 rule three cords issue from the cylinder to enter it. One is immediately 

 below the position of the leaf, and two others arise from a certain distance, 

 passing round and entering the sides of the leaf-stalk. It is these 

 lateral cords from which the stipular cords always arise, and never from 

 the stem-cylinder itself. Hence the anatomy shows that stipules are 

 really part of the leaf, and not independent stem-structures.* 



Besides protecting the bud in the axil of a leaf, stipules may take on 

 the form of bud-scales, and so protect the winter-buds of trees of many 

 kinds. In these the leaf to which any two may belong is not formed. 

 This is the case with the Elm, Oak, Beech, Sweet Chestnut, and Lime. 



The stipules form oval brown scales, overlapping one another. As the 

 bud expands in spring-time they soon fall off, having performed their duty 

 as a protection during the winter. 



In many herbs, especially of hot dry regions, as deserts, the stipules 

 are colourless, and so completely hide the green foliage that the plant 

 looks white or grey. The use in these cases appears to be to reflect the 

 heat and light, so as to protect the more delicate parts concealed from 

 injury by scorching or radiation. 



A remarkable Begonia (B. venosa) and species of Polycarpaa and 

 Paronychia are thus provided with " scarious " stipules. Stipules some- 

 times take the form of tendrils. Such is the case with the Bryony. In 

 this plant the distribution of the cords of the stem is scattered and not 

 in a regular cylinder, being much like those of a monocotyledon. When 

 this is the case transverse cords are thrown out from one to another, 

 making a sort of horizontal plexus. It is from this that the bud and 

 tendril arise. 



In Smilax, a monocotyledon, the tendrils arise with cords from the 

 petiole itself. 



In some plants, as Paliurus australis, the stipules form strong hooks 

 for scrambling, if not climbing purposes, like the hooked thorns of Roses 

 and Brambles. 



In Acacias the stipules form sharp thorns, sometimes of a gigantic 

 size. A. horrida of South Africa thus forms one of the so-called 'Wait- 

 a-bit ' thorny plants, being used for hedges, &c. 



The Bull's-horn Thorn of Nicaragua is remarkable for having its 

 stipules occupied by ants. On the petiole is a large honey-gland, and 

 each of the leaflets develops a pear-shaped little body which supplies them 

 with food. In return for "board and lodging " the ants protect the tree 

 from other species known as " leaf -cutters." These strip shrubs of their 

 leaves, which are cut into fragments and, in Mr. Belt's f opinion, used as 

 hotbeds for growing edible fungi underground. Others think it is only 



* Apparent exceptions arise from greut degradation, as in Violets and Dog's 

 Mercury, &c. 



f Naturalist in Nicaragua, p. 219. This is now proved correct by Alf. Moller. 



