108 HIGH TEMPERATUEE. 



" This result," he says, " did not, in any degree, surprise me ; for I 

 had many years preYiously succeeded, by long-continued very low 

 temperature, in making Cucumber plants produce female flowers only ; 

 and I entertain but little doubt that the same fruit-stalks might be 

 made, ia this and the preceding species, to support either male or female 

 flowers in obedience to external causes." {Sort. Trans, vol. iii. p. 460.) 

 It would seem that among Cucurbits, the power to form pollen iti 

 the nascent floral leaves is increased by heat ; and that being so, to 

 raise the temperature unduly, will have the effect of forming male 

 flowers instead of females ; on the contrary, cold seems to interfere 

 with the formation of pollen, and in that case a low temperature must 

 produce females in preference to males. In what precise way a high 

 temperature acts upon the Cucimiber, we cannot judge of. We see 

 the effects, but we cannot perceive the immediate operation of the 

 cause. It is, however, notorious, as has already been shown (Chap- 

 ter VI.), that there is something at work in nature which does influence 

 the fashioning of leaves into stamens or carpels ; and there is reason to 

 believe that the former are often the result of increased vigour. Thus, 

 in the Hemp plant, the males may be known from the females by their 

 larger size, and greater strength ; and Fir-trees will bear cones^in the 

 feebleness of youth, but not their clusters of stamens, tUl^the tree is in 

 the prime of its age. And it may very well be, that in the case of the 

 Cucumber, the application of unwonted heat may have, and probably 

 does have, the effect of so increasing the vital force, as to throw into 

 the nascent leaves of the flower-buds that quality which results in the 

 development within their cells of the highly organized material called 

 pollen. 



One of our German translators says that in a moist atmosphere, and 

 low temperature, Pelargoniums wUl form little or no poUen, while, 

 under opposite circumstances, even mules produce poUen enough to 

 become fertile. 



Plants, forced in such an improperly high temperature, are 

 soft and watery, with thin leaves, long joints, slender stems, 

 and with no disposition to produce flowers. A slight lowering 

 of temperature affects them more than a much greater lowering 

 would have done under other circumstances; and a permanent 

 abstraction of light readily destroys them. Their inability to 

 decompose carbonic acid, and to assimUate their food in pro- 

 portion to their rate of growth, prevents their becoming so 

 green as is natural to them, and gives them a palhd hue • and 

 if it IS their nature to form other colouring matter, that also is 

 greatly diminished. But, if, with a preternatural elevation of 



