VBGETATrVE ORGANS OF PLANTS. 



283 



and even in certain tribes of Tegetation, like the cacti, 

 which 'have no leaves, to perform the offices of these 

 organs. In general, the functions of the stem are sub- 

 ordinate to those of the organs which it bears — the leaves 

 and flowers. It is the support of these organs, and, it 

 would appear, only extends in length or thickness with 

 the purpose of sustaining them mechanically or provid- 

 ing them with nutriment. 



Buds. — In the seed the stem exists in a rudimentaiy 

 state, associated with undeveloped leaves, forming a hud. 

 The stem always proceeds at first from a bud, during all 

 its growth is terminated by a bud at every growing point, 

 and only ceases to be thus tipped when it fully accom- 

 plishes its growth by the production of seed, or dies 

 from injury or disease. 



In the leaf-bud we find a number of embi-yo leaves 

 and leaf-like scales, in close contact and within each 

 other, but all at- 



tached at the 

 to a central conical , 

 axis. Fig. 45. The | 

 opening of the bud 

 consists in the 

 lengthening of this 

 axis, which is the 

 stem, and the con- 

 sequent separation 

 from each other as 

 well as expansion of 

 the leaves. If t h e 

 rudimentary leaves of a bud be represented by a nest of 

 flower-pots, the smaller placed within the larger, the 

 stem may be signified by a rope of India-rubber passed 

 through the holes in the bottom of the pots. The 

 growth of the stem may now be shown by stretching the 

 rope, whereby the pots are brought away from each 



Pig. 45. 



