16 



.NP^BRASKA STATE HORTICULTURAL SOCIETY. 



urist is that which annually proceeds from the bud. Now a bud is 

 the stunted, inactive end of a shoot, and growth in the spring is 

 simply the resumption of activity. Even the so-called lateral buds 

 are in reality the ends of very short lateral shoots. When the growth 

 of the previous year is checked, at the time that the bud forms there 

 is a considerable deposit of food matter, generally starch, in the bud 

 itself, or near it. On the advent of warm weather the starch be- 

 comes changed to sugar and is dissolved in the water of the tree when 

 it is ready for use by the buds. Each bud, as it becomes sufficiently 

 warmed, absorbs the sugary food and growth at once is resumed ; the 

 stem elongates, thus separating the bud scales and bringing out the 

 young inner leaves. At the apex of the stem new stem and leaves 

 are constantly produced, while below these are as constantly developing 

 into their full grown adult form. For a time the growth at the apex 

 of the stem excels that of the rest of the shoot, but after a time the 

 apical growth diminishes, and, as a consequence, the young leaves be- 

 come bunched at the end of the shoot in the form of a bud. The 

 growth of a stem in length is thus an intermittent one, and the bud 

 is simply the quiescent winter condition of its apex. 



The leaf of the apple tree needs no description as to its external 

 anatomy, as this is well known. Internally, however, its structure is 

 not so generally known. It is composed of very small green cells, 

 surrounded by a skin-layer of colorless cells, and penetrated by a sup- 

 porting framework of branching ribs. The green cells next to the 



upper skin are elongated and closely 

 packed side by side, with one end 

 touching the skin. These are the 

 so-called "palisade" cells of the leaf. 

 In well grown leaves there are two 

 or even three layers of palisade cells. 

 Below these the cells are very loosely 

 arranged, as is well shown in Fig. 

 2. Between all these internal cells 

 there are free spaces which are occu- 

 pied with air and other gases which 

 entered through the breathing pores 



FIG. 2. -Cross section of an apple leaf, mentioned above, and shown in 

 magnified 200 times. Fig. 1. 



