THE LEAF 



83 



Jonquils, Daffodils, and the cylindrical leaf of Onions are other 

 instances. Needle-shaped leaves, like those of the Pine, Larch, and 

 Spruce, are examples. 



LEAVES OF SPECIAL CONFORMATION AND USE 



143. Leaves for storage. — A leaf may at the same time serve 

 both ordinary and special uses. Thus in those leaves of Lilies, such 

 as the common White Lily, which spring from the bulb, the upper 

 and green part serves for foliage and elaborates nourishment, while 

 the thickened portion or bud scale beneath serves 

 for the storage of this nourishment. The thread- 

 shaped leaf of the Onion fulfills the same office, 

 and the nourishing matter it prepares is deposited 

 in its sheathing base, forming one of the concen- 

 tric layers of the Onion. When these layers, so 

 thick and succulent, have given up their store to 

 the growing parts within, they are left as thin and 

 dry husks. 



144. Leaves as bud scales have ah*eady been 

 studied. 



145. Leaves as spines occur in several plants. 

 A familiar instance is that of the common Bar- 

 berry (Fig. 69). In almost any summer shoot 

 most of the gradations may be seen between the 

 ordinary leaves, with sharp bristly teeth and leaves 

 which are reduced to a branching spine or thorn. 

 The fact that the spines of the Barberry produce a leaf bud in their 

 axils also proves them to be leaves. 



146. Leaves for climbing. — The 



leaves of several common climbing or 

 clambering plants, one of which has 

 been figured in another place (page 54), 

 are roughened on the ribs and margins 

 like the stem, as an aid to climbing. 

 Even without roughening, the outstand- 

 ing leaves and side-stems of plants of 

 this general habit support the shoots 

 as they weave their way through the 

 thickets and latticed herbage. It is but 

 a step from the mere resting of the leaf 

 70. Tendril leaves of q^ chance suDDorts to the habit of hook- 



Solanum jas- . 



minoides. ing over them, more or less ; and but 



69. The common 

 Barberry. 



