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. Nature 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 
