BUDS AND LEAVES. 17 



W and to tlie reproductive organs for their needs, receiving back merely 

 what is required for their sustenance and growth. 



BUDS AND LEAVES. 



We have nh-eady seen how the stem and branches elongate by the un- 

 folding of the Inul, the expansion of leaves, and the lengthening of the 

 spaces between the latter, and have noted that the bud exists in the em- 

 bryo. From this time forward it always is the growing point of the plant. 

 Examined in vevtical section, it is shown to be a eolleciion of embry- 

 onic leaves, diminishing in size from without inward. In the growing 

 season the bud is green like the exjianded leaves, though of a more tender 

 shade, but as the end of the season approaches the outer leallets undergo 

 more or less change, including both color and texture, and are not unfre- 

 qnently coated with resinous or gummy matters to protect them against 

 ^1 cold and moisture during the jieriod of the plant's rest. Such altei'ed 

 leallets are termed scales. 



We have already seen how leaves ai'e produced. We will now consider 

 their structure, varied forms, and functions. 

 % Leaves, like stems, consist of woody and cellular tissue, the former col- 

 lected in bundles or fibi'es which form a skeleton whose interstices are 

 filled up with the latter. 



Upon the form of the skeleton, of course, dejiends the shape and gen- 

 rS eral character of the leaf. 



'f The larger and more iirominent fibres of the skeleton are termed 

 veins, the smaller ones veinlets. In leaves having a large central vein, 

 with less jirominent lateral branches, the central one is termed the mid" 

 vein or mid-rib. Indeed, in botanical descriptions the prominent fibres 

 of the leaf skeleton are spoken of as veins, ribs, or nerves indiscrimi- 

 nately, as for example, a leaf is feather-veined, slronglij ribbed, or triiile- 

 . nerved. Little confusion, however, need arise from this misuse of terms if 

 ) the student but remember that though these fibres bear some analogy to 

 veins and ril)s, they bear none whatever to nerves. 



A leaf may commonly be distinguished into two parts : an expanded 

 portion, termed the lamina or blade, and a stalk by which this is at- 

 tached to the stem, termed the petiole or footstalk. In case there be 

 no petiole, the blade being attached directly to the stem, the leaf is said 

 to be sessile. 



Through the petiole, if there be one, or, in its absence, directly into 

 the base of the blade, pass the woody fibres whose ramifications make up 

 the leaf-skeleton. The manner in which the veins ramify is termed the 

 venation of the leaf. 



In endogenous plants these fibres commonly divide at or near the base 

 of the blade into a number of nearly equal branches, which pursue a paral- 



