774 Marvels of the Universe 
HONEY-GLANDS OF ACACIA. 
The base of the compound leaf is here 
show the glands. 
Photos bu | 
“BELT’S BODIES.” 
enlarged to 
[Harold Bastin. 
Leaflets of an Acacia, much enlarged, 
pear-shaped bodies first made known by 
now bear his name, 
Mr. 
to show the 
Belt, 
which 
it#has, in addition, developed special food-bodies 
for the ants which have no analogy in the growth 
of other plants, and apart from their value to the 
ants are of no use whatever to the plant. Every 
small division of the compound leaf has at its ex- 
tremity a little yellow, pear-shaped body growing 
out from it. When the leaf unfolds these ‘“‘ pears”’ 
are not ripe, and they do not ripen all at once, 
but in succession. The ants may be seen going 
from one fruit to another to ascertain their fitness 
for gathering, and on finding one that is ripe, an 
ant nips through the stalk and bears the “ pear ”’ 
off to the nest. 
Belt found that his seedling Acacias, grown in 
his forest garden, though they were visited by 
various local species of ants, were not really tenanted 
by them. These ants knew nothing of the needs 
of the Acacia, nor the price it was willing to pay 
for their protection. They left both thorns and 
“pears”’ alone. The Sauba ant came among 
others, and stripped the plants of their foliage, for 
there were no ant-police to keep them off. Out on 
the savannah, Belt says, he never found one of 
these Acacias that was inhabited by Pseudomyrma 
effectively attacked by the Saubas. One other 
species of ant—Crematogaster—he found inhabit- 
ing the Acacia and nesting in the thorns. Their 
methods differed somewhat from those of Pseu- 
domyrma, for they made their entrance ‘to the 
thorns from the base instead of near the point. 
The photograph on page 771 shows an African 
species of Acacia which has the base of its thorns 
dilated into a spherical chamber which is similarly 
tenanted by a protecting ant. At first the thorns 
are white and soft, then green, and later become 
brown or black and hard. They are bored by the 
ants, who are almost invariably found in posses- 
sion of them. This species is never found to be 
eaten by cattle, and this immunity is believed to 
be due solely to the presence of the ants. 
From all this it is clear that there is so definite 
an understanding between the Acacia and the 
ants, established in the far past and perfected in 
the course of many generations of both plants and 
ants, for their mutual benefit, that this commen- 
salism has now become a fixed habit. To many 
people such an understanding between an animal 
and a plant will be unbelievable ; but strange as it 
may appear, it is true, and it does not stand alone. 
