108 Upon the rate of growth by Plants 



It is probable that these returns will strike different persons 

 differently ; and therefore they are printed at length, and not in 

 the form of an abstract. All such observations are affected by so 

 many circumstances, the exact nature of which it is perhaps im- 

 possible to estimate, that safe conclusions can only be drawn from 

 the average of a large number of facts. The observations made in 

 the course of these experiments amounted to 908 ; a number suf- 

 ficiently large to entitle the conclusions that are drawn from them 

 to some attention. 



As has been already stated the great object of the enquiry was 

 to ascertain at what period in the 24 hours plants in hot-houses 

 grow the fastest, and at which the slowest. The table No. 5, 

 shews that upon the whole this happens in the Afternoon ; but that 

 there is a near approach to the same rate in the Morning and 

 Night, the growth in the one case being 55.11 inches and in the 

 others 49.87 and 49.16 respectively. When, however, we look to 

 the details of these results we find that each of the four plants has 

 its own period of maximum growth, the Vine preferring the early 

 Morning, the Willow the Forenoon, the Passionflower the After- 

 noon, and the Fig the Night. In the Passionflower the preference 

 amounted to something considerable ; and in the Vine to as much 

 as two inches in the course of six weeks ; but in the others it was 

 unimportant. It appears however that in the case of the Willow 

 and Vine, that is to say of the two hardiest of the plants under 

 experiment, the principal growth takes place between midnight 

 and noon, notwithstanding that those are the coldest hours in the 

 twenty four. 



I have not seen the paper of Harting* on this subject, quoted 

 by Munter in his observations on the growth of plants ;f but if, as 



* In the Tydschrift voor Natuurlyke Geschiedenis en Physiologie, by van Hoeven 

 and de Vriese. 



t Botaniche Zeitung, Nov. 3, 1843. 



