Chap. XV. DROSEKACEiE. 355 



power can hardly fail to be beneficial. Nor can the 

 benefit be quite so insignificant as it might at first be 

 thought, for a moderately fine plant of Primula 

 sinensis bears the astonishing number of above two 

 millions and a half of glandular hairs,* all of which 

 are able to absorb ammonia brought to them by the 

 rain. It is moreover probable that the glands of some 

 of the above named plants obtain animal matter from 

 the insects which are occasionally entangled by the 

 viscid secretion. 



Concluding Kemaeks on the Dkoserace^. 



The six kno^va genera composing this family have 

 now been described in relation to our present subject, 

 as far as my means have permitted. They all capture 

 insects. This is effected by Drosophyllum, Eoridula, 

 and Byblis, solely by the viscid fluid secreted from 

 their glands; by Drosera, through the same means, 

 together with the movements of the tentacles ; by 

 Dionaea and Aldrovanda, through the closing of the 

 blades of the leaf. In these two last genera rapid 



* My son Francis counted the planimeter to be 39-285 square 

 hairs on a space measured by inches ; so that the area of both 

 means of a micrometer, and found surfaces was 78 • 57 square inches, 

 that there were 35,336 on a Thus the plant (excluding the 

 square inch of the upper surface flower-stems) must have borne 

 of a leaf, and 30,035 on the lower the astonishing number of 

 surface ; that is, in about the pro- 2,568,099 glandular hairs. Tiie 

 portion of 100 on the upper to 85 hairs were counted late in the 

 on the lower surface. On a square autumn, and by the following 

 inch of both sm-faces there were spring (May) the leaves of some 

 65,371 hairs. A moderately fine other plants of the same lot were 

 plant bearing twelve leaves (the found to be from one-third to one- 

 larger ones being a little more fourth broader and longer than 

 than 2 inches in diameter) was they were before ; so that no 

 now selected, and the area of all doubt the glandular hairs had 

 the leaves, together with their increased in number, and pro- 

 foot-stalks (the flower-stems not bably now much exceeded three 

 being included), was found by a millions. 



