THE VEGETATITB ORGANS OF PLANTS. 



261 



manent, while in others it shortly falls to the ground and 

 grows thereafter horizontally. 



All plants of the higher orders have stems, though in 

 many instances they do not appear above ground, but ex- 

 tend beneath the surface of the soil, and are usually con- 

 sidered to be roots. 



While the root, save in exceptional cases, does not de- 

 velop other organs, it is the special function of the stem 

 to bear the leaves, flowers, and seed, of the plant, and even 

 in certain tribes of vegetation, like the cacti, which have 

 no leaves, it performs the ofiices of these organs. In gen- 

 eral, the functions of the stem are subordinate to those 

 of the organs which it bears — the leaves and flowers. It 

 is the support of these organs, and only extends in length 

 or thickness with the apparent purpose of sustaining them 

 either mechanically or nutritively. 



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

 state, associated with undeveloped leaves, forming a bud. 

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

 its growth is termina-ted 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 embryo leaves 

 and leaf-like scales, 

 in close contact and 

 within each other, 

 but all attached at 

 the base, to a cen- 

 tral conical axis, 

 fig. 45. The open- 

 ing of the bud con- 

 sists in the lengthening of this axis, which is the stem, 

 and the consequent separation of the leaves from each 

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Fig. 45. 



