626 SCALE-LEAVES, FOLIAGE-LEAVES, FLORAL-LEAVES. 



Scale-leaves situated above-ground are found on the buds of all woody 

 plants, both on foliage and floral buds, i.e. both on the lowest portions 

 of those rudimentary shoots which are destined to become leafy shoots, and in 

 those which develop floral-leaves immediately above the scale-leaves. As a rule 

 they present a hard, tough epidermis, are frequently covered externally with 

 adhesive substances, hairs, and the like, and chiefly serve as a protection against 

 the drying up of the little shoot within. When in springtime this axis begins 

 to elongate, they are either immediately detached and thrown off", as in willows, 

 or they may separate just .sufficiently to permit the shoot to grow through, as in 

 Koelreuteria paniculata. In many species they remain undisturbed and unaltered 

 in their position ; in others they separate and remain for some time at the 

 base of the new shoot, as in the Walnut and Ash; whilst in others, again, they 

 are turned back and soon fall off' as in the Mountain-ash (Sorbus Aucuparia), 

 and in most species of the Horse-chestnut {jExculuii). ^scidus neylecta is 

 especially noticeable in this respect, since its bud -scales, which are detached 

 almost simultaneously, are large and red in colour, and when they fall off" they 

 cover the ground under the tree quite thickly as if with autumnal foliage. In 

 most instances the scale-leaves on the buds of woody plants are brown and 

 devoid of chlorophyll, and increase in size only slightly during their separation 

 from one another; those of Gymnocladus, however, have a green colour, and 

 increase in the spring to twice or even three times their former size. 



On the buds of willows only a single scale-leaf is to be seen ; limes have 

 two, alders three, manna -ashes four, while in the beech, hornbeam, elm, and 

 Celtis occidentalis there are very many bud - scales. If only a single scale 

 exists, as in willows, it is deeply hollowed, and surroimds the part of the bud 

 to be protected like a husk. If only a few scale-leaves are developed, as in 

 Gymnocladus, they arch like a dome over the young green foliage-leaves ; but if 

 many, then they lie close above one another like the slates of a roof. It remains 

 yet to be noticed that in all cases where the bud is protected by a single 

 or only a few scale-leaves, their texture is always very tough and hard; but 

 where many are present they are thin and membraneous. It has been 

 previously mentioned that the stipules of many plants, as, for example, of fig- 

 trees, magnolias, and the tulip-tree (fig. 91), take the place of scale-leaves as 

 protective coverings. 



Foliage-leaves, unlike scale-leaves, exhibit an almost inexhaustible variety 

 in their internal structure and external form, a fact partly due, no doubt, to 

 the multifarious duties they have to discharge. The most important of all 

 these functions is the manufacture of organic materials from inorganic food — 

 on the efficient discharge of which the existence, not only of individual plants 

 but of the whole organic world depends. This almost entirelj' devolves upon 

 the foliage -leaves. Of course, in numerous instances cotj-ledons and floral- 

 leaves, the cortex of branches, and in some plants even aerial roots discharge 

 this function ; but all these are so subordinate that we may say that more 



