38 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
OBSERVATIONS ON SOME OF THE PLANTS EXHIBITED. 
By the Rev. Prof. Geo. Henslow, M.A., V.M.H. 
[Delivered March 28, 1899.] 
Alpine Plants. — Prof. Henslow first drew attention to a selection of 
alpine plants exhibited by Mr. Purnell, several of which, such as Gejitians, 
Androsace, Saxifraga oppositifolia, <fec., are remarkable for their brilliant 
colours. This is due solely to the climate, as M. Bonnier, having trans- 
planted several flowering plants from the neighbourhood of Paris to sites 
in high alpine regions and also within the Arctic circle, found that they 
soon assumed similarly bright tints to the plants normally growing there. 
A species of Sempervirum was characterised by having the young central 
bud covered with long hairs growing from the tips of the leaves, giving 
the appearance of cotton wool. He explained that this is a contrivance to 
avoid either a severe chill or too great heat, since it is a bad conductor. 
He mentioned that in the deserts of Africa numerous plants have their 
leaves covered with a felt-like mass of hair to protect them from the 
intense heat. 
In some species of saxifrage exhibited the leaves were more or less 
incrusted with lime. This is the result of an exudation of water from a 
pore in which calcareous matter was dissolved, and then it had evaporated 
on the surface of the leaf. Mr. Henslow observed that some members of 
the Tamarisk family absorb salts of magnesia and calcium and deposit 
them outside ; but as they are highly hygrometric they absorb the heavy 
dews which occur in the hottest months of the year, and so impart the 
water to the plant, which receives no rain for nine months. Thus a group 
of tall Tamarisk trees grows near the edge of the desert outside Cairo, 
but they never receive any artificial irrigation whatever. SoldaneUa was 
interesting as exhibiting visibly the effects of respiration ; for the flower- 
stalk appears through the snow, coming up through a small tube which 
it has dissolved for itself. This is due to the heat produced by respira- 
tion, since all plants respire in order to live, just as animals do, the 
process consisting of the absorption of oxygen by the living protoplasm 
and the emission of carbon dioxide, accompanied by vapour and heat. 
The next point observed was the dwarfing of alpine plants, as shown 
by the above-mentioned plants, as well as by Tlialictrum alpinum, of 
about 6 to 8 in. in height. Mr. Henslow took occasion to record the fact 
that in 1866 he used to collect the English Tlialictrum majiis in a small 
copse on the Surrey side of the Thames, close to Hammersmith Bridge. 
Insectivoeous Plant. — The little Sundew, also exhibited by Mr. 
Purnell, afforded an opportunity of again describing the marvellous 
mechanism of the leaves, which catch insects, then secrete a digestive 
fluid, and so nourish the plant, the chief use being to increase the 
amount of seed produced. 
Gaultheria procumbens, a native of cooler parts of North America 
and covered with scarlet berries, was exhibited by Mr. Ware. It is 
