Retrospective Criticism. I39 



garden has been turned upside down this winter, the whole of the box having 

 been taken up and replanted in a regular manner : 500 cubic yards, equal to 

 as many cart-loads, of marl and loam have been got in for the borders, &c., the 

 greater part of whicli is already trenched in. — W. Exeter, Feb. 11. 1843. 



The Lane-End Horticultural Society, exclusively for the encouragement of 

 horticulture among labouring cottagers, is well worthy of imitation throuo-h- 

 out the country. Premiums are offered for the first and second best cultivated 

 gardens, and for the first and second best of all the commoner vegetables, 

 fruits, and flowers. The premiums vary from \s. to 5s. The place of exhi- 

 bition is the schoolroom, and the clergyman and the schoolmaster are the 

 pnncipal judges. 



The Chislehurst Horticultural Society for Cottagers is conducted on the same 

 general principles as that of Lane-End, and is effecting for part of Kent, 

 what the other is for part of Bucks. Very handsome premiums are given by 

 the Chislehurst Society, and the Messrs. Barnes, and other first-rate gardeners, 

 not only subscribe Hberally, but contribute improved varieties of culinary ve- 

 getables, &c.—^. 7; i^<?i. 1843. 



Art. III. Retrospective Criticism. 



Professor Hcnsloiv's Lecture on Manures. — I have your favour of the 

 27th instant, and the two Ipswich newspapers containing Professor Henslow's 

 lecture on manures, and feel obliged by your attention. I have little to 

 remark on the essay. Professor Henslow is cautious and prudent in his 

 statements, and I agree generally with what he says. A great many, even of 

 jjhysiologists, seem to be of opinion that carbonic acid is the sole way of plants 

 getting their carbon. This, I have no doubt, is the principal form in which 

 they get it, though humic acid and organised substances, I think, cannot be 

 excluded. If sugar, gum, and starch are stored up in the plant, to become 

 again the food of buds in the spring and of seeds, does it not show that these 

 and similar substances may be made useful? When soluble in water, and ab- 

 sorbed, where can be the difference ? In seeds germinating and buds sproutino- 

 these substances are changed into carbonic acid ; which, losing its oxyo-en in 

 the leaf, gives rise to the nascent carbon of DeCandolle, necessary in forming 

 the latex or blood of the plant which alone can furnish the products of assimi- 

 lation ; and what will prevent absorbed substances from being so transformed by 

 the vital activity of the plant, as well as the same substances stored up in the 

 autumn, and restored to the circulation in the spring ?* The professor seems to 

 lean to the opinion that the carbon is mostly taken up by the roots : he says 

 carbonic acid and carbonate of ammonia are got from the air, and that they 

 are absorbed by water, and carried into the soil, which is quite different from 

 getting carbonic acid altogether by the leaves. If the carbonic acid is taken 

 up by the roots, then there is some reason for depositing carbon in the soil ; 

 if wholly got by the leaves, and the atmosphere always contains the same pro- 

 portion, then we may as well spread the carbon on the roof of the house as 

 deposit it in the soil. 



The professor seems to lean to the opinion that manure is best de- 

 posited unrotted. If we were sure of its rotting equally well in the soil, 

 if the moisture and heat of the soil could be regulated so as to insure this, 

 it would be an advantage. The contrary, however, is most often the case ; 



* If organised substances are divided small enough to allow of their entering 

 the spongioles of the root with the water, which they will do if soluble, the 

 decomposing powers of the plant are sufficient to reduce these to the elements 

 of food, as well as sugar, gum, starch, &c. If nascent carbon is needed, as 

 well as nascent hydrogen and oxygen, the carbonic acid of these substances 

 will furnish it as well as that of the soil or air. 



