624 SCALE-LEAVES, FOLIAGE-LEAVES, FLORAL-LEAVES. 



and this is the case not only in wootly plants, e.g. in tlie Oak, as illustrated iu 

 fig. 144* and 144", but also in quite small herbaceous plants, as in the Moschatel 

 {Adoxa Moschatellina), in which small scale-leaves without chlorophjdl, followed by 

 green foliage-leaves, are developed above the cotyledons on the epicotjd, and above 

 these floral-leaves. All the shoots (that is to say, buds) developed later on in 

 perennial plants start below with scale-leaves from which the green blade is absent, 

 perhaps because it would be superfluous. 



The scale-leaves which are developed on subterranean shoots, especially on 

 bulbs, rhizomes, and turions, difler considerably from each other according to the 

 various conditions of growth of these three kinds of shoot-structures. By bulb 

 (bulbus) we understand an erect subterranean shoot, whoso very short, thick axis is 

 covered with relatively long, closely-packed, scale-leaves lying one above another. 

 The resting bulb is really a bud, and its form is occasioned almost entirely by the 

 shape of its scale-leaves. These are in most instances broad and concave, and they 

 are arranged so that the inner ones are completely invested by the outer, as, for 

 example, in tulips and species of onion; and they are elongated, ovate, or lanceolate, 

 and lie on each other like the tiles of a roof, as in the lilies (Liliurn Martagon, 

 album, &c.). The adjacent scale-leaves are sometimes united, as, for example, in the 

 Crown Imperial {Fritillaria imperialis). Those of bulbs function chieflj' as 

 storage-organs. The shoot, whose base they cover, when it begins to develop, 

 withdraws the necessary building materials from this storehouse until its foliage- 

 leaves become green and emerge above the ground; then the leaves are able to 

 manufacture new organic materials in the sunlight. Bulbs are protected against 

 the risk of drying up by the earth surrounding them, but it is very important for 

 them that they should also be protected against the attacks of animals which live 

 underground, and particularly from their nibbling. In addition to the poisonous 

 materials for warding off these attacks, further protection is afforded chiefly by the 

 fact that the exhausted and dead older scale-leaves do not entirely decay and 

 disintegrate, but remain as a sheath. Sometimes they form a tough parchment-like 

 investment, or their tliick reticular and latticed strands remain as a sort of cage, 

 within which the young and succulent bulbs are inclosed and protected, as may be 

 particularly well seen in crocuses, gladioluses, and tulips. 



The scale-leaves also perform the part of storage-tissues in subterranean, 

 horizontally elongating shoots, called rhizomes or root-stocks (rhizovia). They 

 also often serve as protecting envelopes, especially when they cover the apex 

 of the stem as it pushes its way through the ground. In the latter case their 

 cells are strongly turgescent, or more frequently very hard, almost horny, and 

 are folded closely over the apex of the shoot, forming a stiff", pointed cone which 

 is able to penetrate even clayey soil like a borer. 



By turion (turio) is meant a laid originating laterally on underground stem- 

 structures and developing in the summer into a shoot which rises above the 

 ground. In the autumn its upper part dies off', whilst its lowermost, subter- 

 ranean portion persists through the winter and originates new buds. Here 



