ABSORPTION OF RATN AND DEW BY GREEN PARTS OF PLANTS. 171 



being equal to the demand. The absorbing- power is incontrovertible ; 

 but the amount of foliage exposed varies the demand upon the power of 

 imbibition. 



To prove that the absorption and evaporation is not merely mechanical 

 like a sponge, the following experiment will suffice. On June 10 a cut 

 specimen of Nepeta Gleclioma had two leaves wrapped up in saturated 

 blotting-paper. One internode was exposed, bearing two other leaves 

 also exposed to the air. By the 16th the latter were much discoloured. 

 On the 22nd they were nearly dead ; but the buds in their axils had been 

 developing, as well as smaller ones in the axils of the absorbing leaves. 

 By the 27th both buds had borne four leaves each. One absorbing leaf 

 was now dead. On July 10 the other absorbing leaf perished ; conse- 

 quently the buds immediately died. Duration, four weeks and three days. 



4. Experiments to show the Power of Absorption by Leaves and 

 Internodes to Nourish Lower Leaves on the same Shoot. 



The possibility of an internode when wrapped up in saturated blotting- 

 paper nourishing leaves below it has been shown in the case of Symphori- 

 carpus. The following are instances in which the leaves alone or with 

 the internodes did the same. 



A frond of Nephrodium Filix-Mas had the terminal portion wrapped 

 up on July 3. No sign of shrivelling occurred through an intensely hot 

 month until August 22, when a few pinnules began to turn brown. 

 Duration of observation, seven weeks. 



The terminal leaflet of Berberis Aquifolium, as those of Dahlia, 

 Polemonium, Wistaria, &c, all nourished the basal leaflets well for 

 various lengths of time. 



Veronica Chamaedrys, Vinca major, &c, all illustrated the same fact — 

 that upper leaves can act as absorbents to supply lower ones on the same 

 shoot, the lowermost leaves, i.e. those furthest from the absorbing ones, 

 always dying first. Vinca major developed very vigorous axillary shoots 

 from the axils of its absorbing leaves, similarly to the Nepeta Gleclioma 

 described above, the whole lasting six weeks. 



5. On the Nourishment of one Part of a Leaf b\ the 

 Absorption of Water in another Part. 



The objection having been made by Duchartre that, when leaves are 

 laid upon water so that the edges are not touching it, the absorption is 

 merely local, and that water is not transmitted to the border, which 

 consequently dries up, I have tried a large series of experiments, placing 

 (1) the apex only, (2) the basal part, but not the cut end of the petiole, 

 (3) the middle of the blade beneath the water. Both surfaces were 

 immersed in every case. Again, I have taken the same parts, but placed 

 (1) the upperside only, (2) the lower side only on water. The results 

 gave every degree imaginable in the power of absorption. In some cases, 

 g. Ipomoea purpurea, with the lower surface of the apical portion in 

 water, the part in air rapidly perished, as this leaf is particularly thin. 



