214 BOARD OF AGRICULTURE. 



from its carbon and the elements of water, the soluble starch 

 and sugar out of which the tissues of the plant are con- 

 structed ; to exhale the surplus water of the crude sap, and 

 thus aid in its ascension from the s'oil and the roots ; to exhale 

 the oxygen set free in the process of digestion, and thus to 

 purify the air for the respiration of animals ; and, finally, to 

 exhale, at night especially, the surplus carbonic acid liberated 

 within the plant in the process of vegetable respiration, which 

 appears to be as necessary and constant as that of animals. 

 It seems also most probable that the albuminoids, or proto- 

 plasmic substances, are first produced in the leaf, and thence 

 transferred to the various localities, where they are needed in 

 the process of growth. 



To facilitate and control the absorption and exhalation of 

 gases and aqueous vapor, leaves are furnished with breath- 

 ing-pores, or stomates, which open under the stimulus of 

 light and moisture, and close in darkness, or when scantily 

 supplied with water. These stomates are about twice as 

 numerous on the under as on the upper side of the squash- 

 leaf, and the total number is about one hundred and fifty thou- 

 sand to the square inch, or more than one hundred millions 

 on each large leaf. One leaf of the great water-lily, Victoria 

 regia, nine feet in diameter, contains about twenty-four hun- 

 dred millions of stomates on its upper side, and none on its 

 under surface, where they would be useless. 



During the past year much has been written and said about 

 carnivorous plants, which catch great numbers of insects for 

 the apparent purpose of feeding upon them. When a fly 

 alights on the leaf of a Dioncca, the two halves close upon it 

 and hold it fast until consumed, when they open for another. 

 The leaf of a species of Drosera, in New Jersey, is said to 

 have the power of moving towards an insect, fastened within 

 half an inch of it, and feeding upon it. The pitcher-shaped 

 leaves of Sarracenia variolaris not only seem to possess the 

 power of enticing insects to climb from the ground to the 

 inside of their pitchers, by secreting a vertical line of honey 

 on the outside, and also a line around the edge of the cup, 

 but they prevent their escape by an ingenious arrangement of 

 hairs, which continually force them downward as they attempt 

 to fly out. When they thus reach the bottom of their prison, 



