EVAPOEATION OF EVERGKEEN AND DECIDUOUS TEEES. 227 



such a retarding course the root action becomes, if not in ad- 

 vance of that of the branch, at least in action, through an in- 

 creased accession of warmth. Now in this we see a real bottom 

 heat, according to the sense in which " bottom heat" ought to be 

 alone received ; that is to say in its relation to the atmosphere, 

 and not as a specific and absolute condition. Propagators, fruit 

 forcers, and cultivators of all kinds fly to tliis in most emergen- 

 cies ; and it is indeed so important a principle as to be mixed up 

 less or more with all our gardening processes. 



XX. — Report upon some Experiments undertaken at the sug- 

 gestion of Professor Lindley, to ascertain the Comparative 

 Evaporating Properties of Evergreen and Deciduous Trees. 

 By J. B. Lawes, Esq., of Rothamstead. 



In the month of December, 1849, I selected from a nursery 

 garden three plants, each of the twelve varieties named below ; 

 they were fine healthy plants, of a size well adapted for trans- 

 planting ; and although the three plants of a similar description 

 resembled each other as nearly as it was possible to determine by 

 the eye, the nature of the varieties prevented any close agree- 

 ment between plants of a different species. For instance, the 

 Ash, Larch, Oak, Sycamore, had each one stem of small branches, 

 while the two Berberies, the Laurels, the Yew, were bushy 

 shrubs. One plant of each sort was planted in a garden, another 

 was reserved for the experiments to be recorded, and a third 

 was weighed after having the earth washed carefully from the 

 root. The following Table will give some idea of the com- 

 parative size of the plants under experiment : — 



Weight of 

 Plant. 



Spruce Fir 

 Portugal Laurel 

 Evergreen Berbery 

 Yew 



Holly . . . 

 Common Laurel 

 Ilex . . . 

 Larch • 

 Oak . . . 

 Deciduous Berbery 

 Ash . . . 

 Sycamore . 



In ozs. and grs. 

 15 160 

 18 



3 

 22 

 16 

 24 



4 



4 



2 



7 



4 



160 



330 



10 



260 



280 



170 



370 



240 



40 



24 



Weight of 

 Green Leaves. 



In ozs. and grs. 



350 

 132 



1 316 

 9 121 

 434 



k2 



