AND HUE DISTRIBUTION" OF THE STOMATA. 101 



Pass€7'ina liirsuta : the upper surfaces only of tlie leaves liave 

 stomata, aud these surfaces are protected by being pressed closely 

 to the stem or against otlier leaves. 



With regard to the kind of wetting which is prevented by the 

 bloom on leaves, it is probable that it is more effective against 

 rain than against dew, since at least some bloom-protected 

 leaves are easily covered with a coating of dew in very finely 

 divided drops. It is curious to observe the effect of immersion 

 on such a leaf — which may be plunged into water still retaining 

 its coating of dew, and will be found to be perfectly dry on 

 being removed from the water — so that the readiest w^ay of 

 drying such a leaf is to dip it into water. Another fact may 

 perhaps be mentioned as tending, as far as it goes, to confirm 

 the view here advocated — namely, that bloom is frequently ab- 

 sent from the projecting nervatures, though present on other 

 parts of leaves — the nervatures being the parts of leaves on 

 which stomata are not developed. 



Finally, it must be remembered, since bloom certainly has 

 other fnnctions besides the protection of leaves from wetting, 

 that it cannot be expected that every species should show a cor- 

 respondence in the distribution of bloom and stomata. Lund- 

 strom's essav, above alluded to, is of interest in this connection 

 He shows that in some species arrangements exist for the col- 

 lection and distribution and absorption of rain as it falls on the 

 leaves ; and here the surfaces are so modified, by secretions &e., 

 that they are wetted with especial ea^'e. This class of cases 

 must no doubt have a bearing on the subject of the present 

 paper. Such cases as those of TrifoUum repens and Vaccinium 

 Vitis-idceay where the lower surface of the leaf is especially wetted 

 by rain, are of much interest. 



The case of Lobelia Ermtis also conveys a caution. Here, 

 according to Lundstrom, there are small scale-leaves at the base 

 of the flower-stalk which collect the rain on their upper surfaces ; 

 yet it is on these surfaces that the stomata exclusively occur. 

 This case is not in reality opposed to my results, since the 

 stomata function as organs of absorption. 



The results here obtained were woiked out in the year 1878, 



and it was intended to publish them in a work of my father's to 



be devoted to the subject of bloom. I shall on another occasion 



give some account of my father's results, and of some further 



i2 



