278 Vegetable Excretions of Plants. 



Nothing appears to me worse than seeing the large squares of 

 glass, of which nearly all the plant structures in Belgium are 

 composed, cracked and split, in various ways, by the hail and 

 frost. The fact is, from false economy, and to save carpenter's 

 work, almost all the plant houses are composed of squares of 

 about 7 in. broad to 9 in. or 10 in. in length. This looks light 

 and airy at the commencement ; but, after two or three years, 

 the large squares become cracked ; and, instead of taking out 

 the whole square, and replacing it by a new one, the gardeners 

 are satisfied to patch up the fracture with two or three small 

 pieces ; so that there soon is an end to all lightness and beauty 

 about the structure ; while, from the small number of bars, the 

 house is not nearly so strong as one built with smaller squares 

 and a greater quantity of wood. After a severe winter, or a 

 heavy storm of hail, the Ghent green-houses have, for the most 

 part, a curious appearance ; the glass roof resembling a chess- 

 board more than any thing else. 

 Wondelghem, March 8. 1835. 



Art. II. On the Vegetable Excretions of Plants. By J. B. W. 



The newly discovered function of the roots of plants, which 

 is said to be the true cause of the necessity of frequent changes 

 of crops, appears to have engaged the attention of several dis- 

 tinguished horticulturists, some of whom, no doubt, mean to 

 extend their researches farther into this interesting subject. 

 Before any new theory can be received as science, every reason- 

 able objection that can be urged against it ought to be removed. 

 1 will, therefore, state a few facts which, in my opinion, deserve 

 the consideration of those who so strenuously advocate the mo- 

 dern excretory doctrine. 



There are several peach trees in pots in a garden in this 

 neighbourhood, which, the gardener assured me, have not been 

 repotted for more than twenty years ; yet they annually ripen a 

 moderate crop of fruit. These trees are supplied with food 

 by top-dressings of rotten manure, part of which is of course 

 carried down to the roots by the water given to the plants. 

 Now, if the roots of peach trees give out deleterious matter, 

 would not those to which I allude have been " sick even unto 

 death " in less time than twenty years, confined as the roots are 

 to the narrow limits of pots, whence they have no means of escape 

 from its baneful influence ? In another garden is a plant of the 

 double white camellia which has not been repotted for fifteen 

 years : still this plant every year makes young shoots, and pro- 

 duces remarkably fine flowers. I have likewise seen fig trees in 



