184 



THE GREEN-HOUSE. 



use as a substitute for tanner s bark, as a fermenting 

 vegetable substance to produce bottom heat. M'Phail 

 collected indiscriminately whatever leaves came in 

 his way, and he states that the sorts included all those 

 found in modern shi-ubbery plantations; they fer- 

 mented well, and produced mould in which he grew 

 the cucumber, and, with some addition of loam, the 

 melon and pine, to the greatest perfection. M'Phail 

 is the only writer who acknowledges that there were 

 leaves of the pine and fir tribe among those he col- 

 lected ; but the influence of these, he says, if different 

 from that of the common broad leaves of deciduous 

 and evergreen trees, he could not discover. 



From observing the vegetable mould in old pine 

 and fir forests, we are of opinion that this mould is of 

 a different quality from that of the leaves of oaks and 

 other non-resinous plants ; and we think it might 

 well merit the gardener's attention to select a quantity 

 of this mould, keep it by itself, and try whether in 

 the culture of heaths and terebinthinate plants it 

 would not be a good substitute for moor earth. 



Mould of rotten dung is another requisite in the 

 culture of green-house plants. This is easily formed, 

 by bringing together, in a heap or ridge, a quantity 

 of old hot-bed dung, or spit dung of any sort, and 

 turning it over occasionally for a year or more till it 

 becomes a soft black mould. There are three va- 

 rieties of mould of dung which ought to be obtained 

 if convenient, and in the compost ground ought to be 

 kept quite distinct. 



