Iiifiuence of Climate on Cultivation. 
497 
%"arieties yield more abundantly, from the fact of the succession 
of fresh and vital leaves continuing to absorb food from the atmos- 
phere. Early varieties of peas must be more liberally manured, 
as a compensation for the shorter period of their growth. 
We have thus endeavoured to give a rough outline of the 
general influence of climate on the most important of our agri- 
cultural crops, as well as of the different practices to which they 
lead. The subject has been, as far as possible, divested of its 
strictly technical or scientific treatment. Many interesting pro- 
blems are yet to be solved in this branch of agricultural science. 
We shall conclude by a recapitulation of the climatic influences, 
which, in different degrees of intensity, seem to be common to all 
plants. 
1. The leaves of plants seem to have greater powers of ab- 
sorbing carbonic acid and ammonia from the atmosphere during 
the warmest season. 
2. Plants absorbing more atmospheric food during the warm 
season require, therefore, less manure in the soil to assimilate 
a given amount of produce. 
3. Heat and moisture thus become so far a compensation for 
manures yielding carbonic acid and ammonia. 
4. But, as heat imparts greater vitality to plants, it enables 
them not only to take more of food from the atmosphere, but to 
work up a larger quantity applied to their roots. 
5. A high temperature, accompanied by a moist atmosphere 
and an abundance of manure yielding ammonia, retard the 
flowering of most cultivated plants. 
6. On the other hand, a dry atmosphere and soil, a low tem- 
perature, and a deficient supply of food within the soil, all tend 
to hasten the flowering and seeding of plants. 
In dry soils and climates manures containing nitrogen are ren- 
dered more potent in their effects when applied in the form of 
vegetable matter. Like a moist atmosphere, the vegetable matrix, 
to a certain extent, compensates for physical deficiencies of soil. 
XXVIII. — On the Kohl-Rahi. By Peter Lawson and Son, 
Edinburgh. 
Deab Sir, EcL'nbur^b, 14th Jan., 18G0. 
In sending you the following paper on the Kohl-Eabi, we think 
it right to state, that oiu- ovra experience of it is confined to the culti- 
vation of the different varieties, and to the gi'owth and management of 
the crop on the gi-ound. As you expressed a desire, however, for in- 
formation on other points, we have taken some pains to j^rocme it 
from tmstworthy som-ces, all of which are specially indicated when 
they have been made use of. 
VOL, XX. 2 K 
