STEMS 67 



ability is of great advantage to plants, the vernal habit may 

 be mentioned. It is a matter of common observation that 

 the rich display of spring flowers occurs in forests and 

 wooded glens before the trees come into full foliage. The 

 working season of these spring plants is between the begin- 

 ning of the growing season and the full forest foliage, and 

 the subterranean shoots enable them to send up branches or 

 leaves with great rapidity. After the forest leaves are fully 

 developed, the available light for work beneath the forest 

 crown diminishes, the spring flowers disappear, and the short 

 period of activity does not return until the next season. 



It has been observed that many of these underground 

 structures gradually become more and more deeply buried, 

 .and it appears that some process of self-burial is going on. 

 For example, it has been observed that if the tuberous 

 underground stem of Jack-in-the-pulpit, often called In- 

 dian turnip, be planted in a flower-pot near the surface of 

 the soil, it will be found six inches deeper within a week. 

 This is probably an illustration of exceedingly rapid burial, 

 but enough has been observed of the habits of such plants 

 to indicate that such gradual self-burial of underground 

 parts is very common. Experiments have indicated that 

 this self-burial is not continued indefinitely, but that for 

 each kind of plant there is a normal depth reached by the 

 underground stems. If such stems are planted below 

 their normal depth, the experiments show that there are 

 various methods of ascending to the proper depth. 



BUDS 



.28.. Mature of buds. A bud is an undeveloped shoot, 

 whose internodes have not elongated, so that the leaves 

 overlap, forming a more or less compact structure (Fig. 66). 

 It resembles a bulb or bulblet in general structure, except 

 that the overlapping leaves are not thickened as food 

 reservoirs. The outer (older) leaves of the bud protect the 



