FEBRUARY. 41 



are as essentially necessary to the germination and early growth of 

 plants as the luminous rays are, at a further stage of their progress, to 

 enable them to decompose carbonic acid, and assimilate the carbon fur 

 their use ; and that neither actinisfn nor the luniinous principle are of 

 themselves sufficient to perfect the growth of plants, or to induce the 

 power of reproduction, which is mainly effected by the caloric or heating 

 rays, these latter having a tendency to produce that change in the planfs 

 system which ends in the production of flowers and fruit. 



In reference to this, one of the most scientific writers of the present 

 day says : — " Observations which have extended over many years, 

 prove that with the seasoils the solar powers are, relatively to each 

 other, subject to an interesting change. In the spring, the actinic power 

 prevails, and during this period its agency is required for tlie develop- 

 ment of the germ. As the summer comes on, the actinic rays diminish, 

 and those of light increase. We see the necessity for this, since luminous 

 power is required for the secretion of carbon, with which the woody 

 fibre is formed, and also the proximate principles of the plant. Autumn, 

 the season of fruit, is characterised by an increase of the heat rays and 

 a diminution of the others ; this change being necessary, as science now 

 teaches us, for the production of flowers and fruit." — Poetry of 

 Science^ hy Robert Hunt. 2nd ed. 



INIuch as I admire the writer, I have doubts whether thi^ attempt at 

 generalising the phenomena alluded to is altogether correct. In fact, 

 the forcing of flowers and fruits, whereby the blooming of plants and 

 ripening of fruits takes place at seasons the opposite of that in wdiich 

 they occur when not subjected to artificial treatment, goes to prove, 

 either that the separate offices or powers of the three principles — the 

 chemical, luminous, and heating — on vegetation, at different stages of 

 the plant's growth, are over-rated ; or, that plants themselves, at any 

 season, according to their period of growth, exercise an influence in 

 inducing a preponderating power in those rays which at the time are 

 essential for the due fulfilment of their functions. This power may be 

 reciprocal, according to the age of the plant, or rather, in accordance 

 with its secreting power ; for no doubt can be entertained, but that the 

 power of assimilation changes with the age of the organ by whose 

 agency it is effected. On what principle besides are we to account for 

 the ripening of Grapes in March, or Peaches in April, or the blooming 

 of Roses and Pelargoniums in February, a;:d numerous other instances, 

 familiar to every gardener ? 



J. S. 



(To he continued.) 



