PROF. THISELTON DYER ON SCIENTIFIC HORTICULTURE. 13 
given to these always indicated both the hybrid origin and the 
parentage. 
There is one branch of science intimately connected with 
horticulture in which we are far from reaping at present the 
practical benefit of knowledge. This is meteorology. It is too 
• much, I am afraid, to hope that we shall ever possess the slightest 
control over the asperities of weather, but it is scarcely too much 
to look forward to improved methods of foretelling what is in store 
for us, as well as improved methods of obviating its efi'ects. The 
study of careful records of daily observations will, no doubt, 
eventually reveal not only some of the causes that influence 
weather itself, but will also throw light upon changes in public 
health, with which it cannot be doubted that weather is closely 
bound up. Such records the Royal Horticultural Society kept at its 
Chiswick Garden for forty-four years, and the results of the observa- 
tions have been lately printed by Mr Glaisher at the Society's 
expense. The practical information which can be deduced from 
this volume is not, perhaps, considerable ; it is, however, a contri- 
bution to the accumulated stock of records which will one day find 
their utilisation. 
The mean temperatures at Chiswick, as deduced from the whole 
observations oi" forty-four years, starts from its lowest point of 35*8 
deg. on Jan. 6, and rises more or less gradually to its highest, 64*4 
deg., on July 17. If climate would only pursue this even course 
with some approach to constancy, vegetation would follow it with a 
clockwork regularity. We know, however, to our cost, that it 
does not do so, and very considerable deviations take place to one 
side or the other of the mean temperature. Both are injurious. 
A premature development of vegetation lays it open to subsequent 
injury, and comes to much the same thing, as regards its efi'ects, as 
a late frost. 
"What the horticulturist really has to fight, then, are the effects of 
cold. The precise mode in which plants are affected by it is 
hardly completely known. In many cases, no doubt, the vital 
properties of the protoplasm contained within the cells receive an 
injury from the direct effect of low temperature from which there 
is no recovery. In other instances death is not the inevitable result 
even from freezing ; but, as is well known, if thawing be gradually 
effected, no great harm will be suffered. Some curious experi- 
ments published by Eecquerel appear to show that cold below the 
freezing-point, like the temperature of boiling water or the electric 
discharge, produces an alteration in the cell walls, which renders 
