NOTES ON TREE PLANTING AT SAN JORGE, URUGUAY. 229 
plough among them. And in every plantation of trees grown 10 
feet apart, I have continued this practice of sowing three rows of 
maize for two years, partly for nursing purposes, and partly to 
recoup my expense in ploughing and fencing the land. I have 
also latterly sometimes sown two rows of maize only in the third 
year. 
Damages to plantations, except from droughts and frosts, are 
not numerous. The black leaf-cutting ant is certainly the worst ; 
and it is only by choosing for planting the trees not greatly affected 
by them, that this trouble may be almost avoided. However, 
even with trees that greatly suffer from the black ant, success 
may be obtained, but at an enhanced cost. Ants of course do 
their damage in the early years of a tree’s life, and protection 
may be afforded a tree by isolating its trunk from the surrounding 
ground with a 4 inch wide zinc cylinder, 6 inches high, with a 
2 inch “brim” soldered to the top of the cylinder at an angle of 
45°; the ants cannot turn the angle where the brim is united to 
the cylinder. 
Other mechanical devices are used to keep the ants from getting 
at a young tree stem, all troublesome, all more or less expensive, 
and all requiring attention, to see that no casual bridge is formed 
anywhere.1 The radical cure is extirpation of the ants ; and 
though that can be done where there are many neighbours, all 
helping, in valuable land near towns, it is impossible in the open 
country—and even the destruction of nests is expensive, though 
we do it in the neighbourhood of seed-beds of the gardens and 
orchards, etc. This ant cuts off and carries to its nest leaves and 
twigs at its own discretion, carefully discriminating between 
classes of plants; it is my belief that all this harvest is stored 
in the subterranean nests, and subsequently devoured, and 
that probably after having undergone some fermentation. For 
this idea of the necessity of fermentation I am indebted to a 
friend, a doctor, and most observant man, who lived for some 
years on San Jorge land. It is certain that ants like working in 
early morning whilst the dew lies, desist during the hot hours of 
the day in summer, and are most noticeably active just after a 
shower. In winter they do not work until the frost has quite 
disappeared. When a nest has-been destroyed, in the efficient 
way in which we do it, some ants certainly escape, perhaps chiefly 
1 Cyanide of potassium and other poisons are useful to keep down their 
numbers. 
