The Dispersal of Seeds by Ants. 
adhered to the seed to render them attractive. That the elaiosome 
itself is a desirable object to the ants, was easily proved by placing 
some of the detached caruncles in the pathway and these were 
readily carried away, when once they were observed. But being 
very small they were more often overlooked, and this fact would 
indicate, as indeed the previous experiments had done, that the 
elaiosome does not attract the ants by any special odour or scent. 
When I first made the suggestion that the orange-coloured 
caruncle of Ulex acted as a food-body or elaiosome for ants, it was 
pointed out to me that the broom (Sarothamnus) possessed a very 
similar caruncle which must probably serve the same purpose. 
Though I know of no striking cases illustrating the dispersal of the 
broom along disused roadways such as I have instanced in the case of 
the gorse, yet I noticed, as mentioned above, a young plant of 
Sarothamnus at Fairbourne which could not have owed its position 
to the mere dehiscence of the pod, as the nearest presumptive 
parent was at least twenty feet away and on the other side of a 
stone wall. Ants on the other hand could have readily effected the 
dispersal. I consequently made some experiments with the seeds 
of the broom, similar to those I had made with the gorse-seeds. 
On September 20th, I placed five seeds of the broom on an 
ant-track leading to one of the nests with the following result:— 
6’7 ... ... ... ... 5 seeds 
6-10 
6-14 
6-16 
6-21 
6-25 
4 seeds remained 
3 ,, ,, 
2 „ 
1 >* >> 
0 „ 
In other words the five seeds had been carried away in eighteen 
minutes, and the behaviour of the ants had been identical with that 
exhibited when they found the seeds of the gorse. They turned 
the smooth seeds about and when they found the food-body they 
rarely let go, biting and tearing at the elaiosome and finally carrying 
the seeds bodily away. 1 
The above experiments leave it uncertain whether the ants 
actually get any large quantity of the seeds they carry away to 
their nests or whether they manage to sever the elaiosome from 
the seed on their way. Judging from Sernander’s investigations 
probably some remain by the roadside while some are actually 
taken to the nests. On one of the ants’ nests examined, there were 
1 Mr. A. G. Tansley tells me that he has observed the distribution 
of the broom together with the gorse along an old cart track 
overgrown with heather on a large heather-moor near Rievaulx 
Abbey in the North Riding of Yorkshire. 
