FREE BOOKS

Author's List




PREV.   NEXT  
|<   146   147   148   149   150   151   152   153   154   155   156   157   158   159   160   161   162   163   164   165   166   167   168   169   170  
171   172   173   174   175   176   177   178   179   180   181   182   183   184   185   186   187   188   189   190   191   192   193   194   195   >>   >|  
lants, growing in boggy land over pretty much the whole world. They are represented in the United States by several species of sundew (_Drosera_), and the still more curious Venus's-flytrap (_Dionaea_) of North Carolina. The leaves of the latter are sensitive, and composed of two parts which snap together like a steel trap. If an insect lights upon the leaf, and touches certain hairs upon its upper surface, the two parts snap together, holding the insect tightly. A digestive fluid is secreted by glands upon the inner surface of the leaf, and in a short time the captured insect is actually digested and absorbed by the leaves. The same process takes place in the sundew (Fig. 104, _N_) where, however, the mechanism is somewhat different. Here the tentacles, with which the leaf is studded, secrete a sticky fluid which holds any small insect that may light upon it. The tentacles now slowly bend inward and finally the edges of the leaf as well, until the captured insect is firmly held, when a digestive process, similar to that in _Dionoea_, takes place. This curious habit is probably to be explained from the position where the plant grows, the roots being in water where there does not seem to be a sufficient supply of nitrogenous matter for the wants of the plant, which supplements the supply from the bodies of the captured insects. [Illustration: FIG. 105.--Types of _Aphanocyclae_ (_Cistiflorae_). _A_, _B_, leaves of the pitcher-plant, _Sarracenia_ (_Sarraceniaceae_). _A_, from the side; _B_, from in front, x 1/2. _C_, St. John's-wort (_Hypericum_), x 1/2. _D_, a flower, x 1. _E_, the pistil, x 2. _G_, cross-section of the ovary, x 4. _H_, diagram of the flower.] Similar in their habits, but differing much in appearance from the sundews, are the pitcher-plants (_Sarraceniaceae_), of which one species (_Sarracenia purpurea_) is very common in peat bogs throughout the northern United States. In this species (Fig. 105, _A_, _B_), the leaves form a rosette, from the centre of which arises in early summer a tall stalk bearing a single, large, nodding, dark-reddish flower with a curious umbrella-shaped pistil. The leaf stalk is hollow and swollen, with a broad wing on one side, and the blade of the leaf forms a sort of hood at the top. The interior of the pitcher is covered above with stiff, downward-pointing hairs, while below it is very smooth. Insects readily enter the pitcher, but on attempting to get out, the smooth, slip
PREV.   NEXT  
|<   146   147   148   149   150   151   152   153   154   155   156   157   158   159   160   161   162   163   164   165   166   167   168   169   170  
171   172   173   174   175   176   177   178   179   180   181   182   183   184   185   186   187   188   189   190   191   192   193   194   195   >>   >|  



Top keywords:
insect
 

leaves

 

pitcher

 

curious

 

captured

 
species
 
flower
 

digestive

 
process
 

pistil


surface

 

sundew

 
Sarraceniaceae
 

Sarracenia

 
States
 

supply

 
smooth
 
United
 

tentacles

 

Similar


differing

 

appearance

 

sundews

 

plants

 

habits

 

purpurea

 

Illustration

 

Aphanocyclae

 

Cistiflorae

 

Hypericum


section

 
diagram
 

summer

 

interior

 

covered

 
downward
 

attempting

 
readily
 

pointing

 
Insects

swollen
 

rosette

 
centre
 
arises
 

northern

 

insects

 
reddish
 

umbrella

 
shaped
 

hollow