980 ~ NOTES ON THE BOTANY OF JAMAICA. 
observed at all was on the Yallahs River; but it does not pay. In 
St. Anne's parish, in the north, it is, after cattle-farming, the main stay 
of an estate. 
The mode of making a pimento-walk, throws some light on the 
succession of crops in forest-trees, so remarkable in America. If the 
ground is kept cleared, the grass will grow up and stifle the young 
plants. It is necessary to permit the wild bushes to remain, and thin 
them out from time to time, always leaving enough to shade the 
pimento, until the young plants have acquired strength to shift for 
themselves, and they are then allowed the exclusive occupation of the 
ground. The elegant Tetrazygia Fadyeni (Hook. in Kew Garden 
Miscellany, 1849, t. 12), which seems to require exactly the same 
rocky soil and climate as the pimento, is often spared for ornament 
where the proprietor resides on his own estate, and but for the taste 
of these gentlemen would probably have been extirpated. It is a 
plant most difficult to rear in any other situation. Mr. W. Stewart, 
of Green Park, after many ineffectual attempts, only succeeded at last 
by bringing away a portion of the rock attached to its roots. Thus, 
without any exhausting of the soil or change of climate, the indi- 
genous trees of a country may be unable to grow up for a certain 
period for want of companions belonging to very different genera, and 
may chance to be entirely superseded and driven from their native 
haunts by introduced exotics. 
Among intruders of this kind, the most conspicuous are the Mango 
and Guava. The latter seems to be propagated by the pigs, which, 
after tearing up the ground in search of roots, drop the undigested 
seeds of the Guava into it. This shrub prefers low swampy places 
that are inundated in the rainy season, and affords food and shelter to 
thousands of rats, which build like squirrels in its branches. The 
rat is supposed to be the common European one, and to have been 
brought here in ships; but the head is much more elongated and 
pointed, and the fur more shaggy. When hunted with dogs, it takes 
refuge in the * sink-holes," where it is impossible to follow it. Dogs 
are often lost in these subterranean caverns, which must be of great 
extent, as the water flows out below in a uniform stream, and perfectly 
clear, let the rains have been ever so heavy, or the drought of long 
~ continuance. 
In the same way as the pigs propagate the Guava, the bullocks disperse 
