430 Transactions of the Boyal Society of South Africa. 
while the twig weighed only 9'011 originally, it does not appear possible 
that this amount, which is equal to 9*2 per cent, of the weight of the twig, 
could have been contained in the hairs only, and that nothing of it should 
have passed into the tissue of the leaves. 
In the case of Mesemhrianthemum barbatum a drop of water was placed 
daily on the stellate hairs, and yet a twig, weighing originally 0*391, lost 
0-109 in 7 days, or 27'9 per cent, of its weight. Here again the experi- 
mental conditions differ widely from those existing in nature, where the 
hairs would have, during 4 or 5 months of the year, at least 10 hours 
every night for carrying on the absorption of dew. Further, the specimens 
experimented with must have been in a very luxuriant condition, being 
probably from garden plants, for a twig of Mesembrianthemum barbatum 
taken by me from a wild plant gathered a few days before in the Karroo 
and kept in the laboratory for 7 days, during which the midday tempera- 
ture was about 25° C, lost only 9*7 per cent, of its weight. Cultivated 
plants of Mesembrianthemum barbatum are, however, less suitable for 
such experiments than wild plants, for they wither much quicker, and 
their stellate hairs have lost much of their power of absorption. The 
hairs are mostly smaller, often less in number or quite absent. 
Having carried out numerous experiments * with several species of 
plants some time ago, but with specimens brought directly from the 
Karroo, I had come to the conclusion that these plants are able to absorb 
appreciable amounts of water by means of specially constructed organs, 
viz., hairs, stipules, or aerial roots. I shall quote only one of these 
experiments here. A leaf of Grassula tomentosa, weighing 28'67, was 
kept in the laboratory for 3 days, when it had lost 0*7 grammes. By 
placing the leaf every night into the open, thus exposing it to the dew, 
while during the day it was kept in a cardboard box, it regained its 
original weight in 12 days, although it must have lost some more water 
by transpiration during that time. 
A few additional experiments were made by me recently, selecting 
Mesembrianthemum densum for the purpose, as the structure of the 
stellate hairs of this species is quite similar to that of M. barbatum^ of 
which I had no suitable specimens at my disposal. The leaves lend 
themselves well to such experiments, for they may be suspended in such 
a way that the apical hairs only touch the water, while the remainder of 
the leaf remains quite dry. In each case some young pairs of leaves were 
chosen, and having been kept in the laboratory for a few days to allow 
them to lose a little water by transpiration, two of them were suspended 
in a beaker side by side, in order to make sure that both were surrounded 
by air of equal relative humidity. One was a little above the water, the 
* A full account of these experiments is given in Marloth, " Das Kapland," Jena, 1908, 
pp. 303-309. 
