132 
INFLUENCE OF CLIMATE ON PLANTS * 
SOLAR HEAT. 
CoNiSECTED with tliG growtli of plants, and constituting, in fact, an epocli 
thereof, is the development of their blossoms, and the formation and maturation of 
their fruit and seed. Heat is essential to the due performance of these functions, 
especially of the latter, and hence it is that many exotic plants seldom, in this 
country, produce flowers ; the temperature being inadequate, or not sufficiently 
uniform and continuous. 
Various modes of accounting for the infertility of plants have been adopted by 
different authors, among which, a consideration of the quality of the soil appears 
to have obtained a prominent place. There can be no doubt that soil exercises a 
considerable influence on vegetable production ; but it seems to have been for- 
gotten that, unless possessing peculiar properties, it is not so much the chemical 
composition, as the capacity for the retention or circulation of fluids, which renders 
it inimical or congenial. The importance of light in promoting fertility has before 
been insisted on ; this agent is, however, chiefly requisite for the plants of tempe- 
rate climates, as the majority of tropical species do not luxuriate beneath the 
immediate beams of the sun, but have shade afibrded them either by surrounding 
vegetation, or the dense vapour of the superincumbent atmosphere. 
Moisture is so intimately concerned with heat in the elaboration and develop- 
ment of the fruitful organs, the degree of each being increased by the absence of 
the other, and diminished by its presence, that it is absolutely necessary (though 
contrary to the plan we have proposed to ourselves) to notice the reciprocal 
operation of both these agents in the present place. We shall not attempt to 
investigate the diflereut members of flowers, or the manner in which they are 
formed, but merely state the conditions most favourable to their production. On 
the former point, physiologists promulge such extremely diverse hypotheses, that 
the unsophisticated inquirer after truth feels himself strangely confounded and 
perplexed by perusing the works of antagonist authors. 
That flowers are distinct organs, fulfilling definite and necessary offices, appears 
indisputable. Like all other parts of a plant, they are, however, subject to 
remarkable changes, according to particular circumstances, and their development 
is also determined by atmospheric conditions. It is by neglecting to consider, 
compare, and associate these very palpable positions, or by regarding either of 
them too exclusively, to the virtual suppression of the other, that the diflbrences of 
physiological writers on this question have been occasioned. 
Growth, and the production of seminal organs, are obviously difi*erent processes, 
and require individually the application of particular agents, or, more strictly 
* Continued from page 1 10. 
