82 



ELEMENTARY BOTANY. 



Fig. 115. 



then digested by the acidulous secretion, which is at such 

 times more copiously poured forth. The nutritive portion is 

 absorbed by the plant and thus furnishes a portion of its 

 (nitrogenous) food. Venus's Fly-trap (Fig. 115), the lobes of 



whose leaves quickly close and 

 capture insects when the latter 

 touch the slender hairs on the 

 upper side, is likewise capable 

 of digesting animal food. The 

 numerous sessile glands provide 

 the digestive secretion, and also 

 absorb into the plant the di- 

 gested portions of the insects. 

 Glands, whose viscid secretion 

 is capable of digesting nitro- 

 genous material, are also found 

 on the leaves of the Butterwort (Pinguicula), which grows on 

 wet rocks and damp soils. The curious little bladders of the 

 Bladderwort (Utricidarin) capture small water animals. In 

 the pitcher-leaves of Sarracenia and Nepenthes, insects fall 

 and drown ; these animals, by their decay, probably furnish" 

 some food to be absorbed by the plants. 



16. A portion of the elaborated food, or plastic material 

 as it is called, is consumed at once at the points where growth 

 is taking place. In the earlier or vegetative stage of the plant 

 all of it may be consumed immediately. But there is in 

 plants generally an excess which is then stored up for future 

 use. It is called reserve material. During the reproductive 

 period in the life of plants a large portion is laid up in the 

 seeds and spores. It also accumulates in roots, tubers, bulbs, 

 rhizomes and stems. In case of the deciduous shrubs and 

 trees the food material passes from the leaves into the twigs 

 at the close of the growing season. Then a separative layer 

 of cells is formed at the base of the leaf and the latter conse- 

 quently severs its connection. The scar that remains is not a 

 wound, since the exposed cells are cutinized and rendered 

 impervious to fluids, In the following spring the growth is 



