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V. Notes made in the Garden of the Horticultural Society 

 upon the rate of growth by plants at different periods of the day. 

 By the Vice Secretary. 



(Communicated by the Garden Committee.) 



The great differences that occur in nature between the relation 

 of plants to the atmosphere, at different periods of the day, do not 

 appear to have often suggested the necessity of observing the 

 degree in which vegetation is affected by such circumstances in 

 their rate of growth. And yet we must suppose that the develope- 

 ment of a plant under the influence of a bright sun, or in a damp 

 and clouded atmosphere, in a cool night, or in a chilly morning be- 

 fore sunrise, will be materially dissimilar. It is in very few cases, 

 however, that physiologists have turned their attention to such 

 variations. For this reason, and more especially because the 

 operations of the forcing gardener are very much connected with 

 the enquiry, a series of observations upon the subject was made 

 four times daily, in the Garden of the Society, by Mr. James 

 Donald, during the months of March and April 1843. 



The plants selected for Experiment were a Sweet willow (Salix 

 pentandra), a Fig, the Onyx Passionflower, (Passiflora onychina), 

 and a Vine. The place in which the observations were made 

 was a damp curvilinear stove, used for the cultivation of tropical 

 plants; its average temperature being 69°; that is 73° by day 

 and 65° by night. The plants were fastened as they grew, to a 

 lath, on which the amount of lengthening was marked off four 

 times a day, viz. at 6 A.M. ; Noon ; 6 P.M. ; and 11 P.M. 



