432 
Transactions of the Boyal Society of South Africa. 
organs of absorption. The amount absorbed may not be large, but if a 
leaf is able to supply itself, at least during some stages of its life, such a 
gain must be of importance to plants living under such extreme conditions. 
The negative results obtained by Dr. Schonland with solutions of 
eosin, when the hairs only were stained but not the tissue of the leaf, do 
not disprove the diffusion of water into the tissues. Water passes through 
cell walls much more readily than anilin-dyes. Seedlings of wheat or 
maize kept in water-cultures to which eosin has been added will, even 
after several days, show the staining only in the root-hairs and the 
epidermis-cells, but not in the central parenchyma nor in the vessels, 
although the shoot may have grown several inches during that time, and 
the roots had obviously absorbed a corresponding amount of the solution. 
The same phenomenon is also easily observed by suspending a strip of 
filter-paper in such a solution, when the water invariably rises much 
higher than the dye. 
In addition to the experiment with Crassula tomentosa referred to 
above, I have recently made the following one : A young leaf, weighing 
1*76 grammes, was kept in the laboratory during the month of June 
(temperature low, humidity of air high) for 10 days, when it weighed 1-41, 
having lost during that time 0-35, or 0-035 grammes per day. It was then 
immersed in water with the fringe of the apex for 12 hours, and found to 
weigh 1-69, having gained 0*28, which means that the leaf had, during 
one night, made good the loss experienced during 8 days by transpiration 
and evaporation at the cut end. 
There is consequently no doubt that this plant, and, I conclude, 
various other succulents of our arid regions, are able to utilise the dew 
deposited on their leaves. I agree with Dr. Schonland that the marginal 
papillae of Crassula cymosa and allied species are not capable of absorbing 
moisture. Some species may not be able to do so at all, but in others the 
leaves can do it, whether by means of specially constructed hairs or 
through the water-stomata would not matter. It is quite possible that in 
some species the latter mode prevails, and that the hairs and papillae assist 
merely mechanically by retaining the drops of dew, which otherwise would 
run off too quickly. In either case the gain is so considerable that it 
cannot be without advantage to plants living in regions with a very scanty 
rainfall. 
Summary. 
The anatomical structure of the apical hairs of the leaves of Mesem- 
briafithemum densum, Haw., and M. barbatum, L., show them to be well 
adapted to the absorption of water, at least in the younger state of 
the leaf. 
