LECTURE ON SPRING FLOWERING PLANTS. 355 



and winter. The leaves decompose carbonic acid during 

 the day, liberating the oxygen, which they re-acquire 

 during the night. But winter is their longer and more 

 complete period of rest, although the roots are supposed to 

 be never wholly inactive except when frozen. Now this 

 state of rest, which is of vital importance to plants, may 

 be brought about equally by the agency of cold or 

 drought. Deciduous trees lose their leaves by the frost 

 on the approach of winter ; bulbous plants fall into a 

 dormant state by the drought of summer; and they equally 

 attain, although by different and opposite agencies, the 

 necessary state of rest. While it is possible to change the 

 seasons which we do in forcing without injury to the 

 plant, it is important not to annul or intrench too far on 

 any one of them. Spring, summer, autumn, and winter, if 

 changed as to date, must still be allowed to follow in 

 due succession, or the health of the plant cannot be 

 maintained. 



I have judged these few remarks necessary in order 

 to render clear what is about to follow. I shall not, 

 however, enlarge on these physiological questions, because 

 the lectures of Dr Masters, the first of which I was 

 fortunate enough to hear last Saturday, will no doubt 

 explain them with a skill and lucidity that I cannot 

 hope to reach. 



I shall now pass on to consider certain principles in 

 the art of forcing, on the due observance and application 

 of which success depends. To elucidate my views I shall 

 take a single plant as an example, selecting for my pur- 

 pose the Rose. If a Rose is taken from the ground in the 

 autumn, before the natural period of rest has expired, and 

 suddenly thrust into the forcing-house where a high 

 temperature is maintained, growth will quickly re-com- 

 mence, and flowers follow in due course, but both leaves 

 and flowers will be feeble, and of indifferent quality. On 

 the contrary, had the plant been previously rested, both 

 leaves and flowers would have been fully developed. 



