ACACIA SPH^ROCEPHALA AND CECEOPIA PELTATA. 405 



which terminates above in a sharp point. When the sheath of 

 the leaf is nearly open, pestle-shaped bodies develop in the 

 cushion ; they are from -8 to 1 millim. in length, and from '3 to 5 

 in breadth ; the free end is rounded ; and the point of greatest 

 thickness takes various positions ; so that they may be either egg- 

 shaped, cylindrical, or pear-shaped. "When ripe they are milk- 

 white and rather translucent ; on drying they become yellow- 

 ish and shrink somewhat. As they ripen they project beyond 

 the hairs. They now break off at the slightest touch, and ulti- 

 mately fall out spontaneously. The growth of fresh bodies con- 

 tinues for several weeks ; and on an Imbauba tree that has not 

 been visited by ants, as many as sixty or a hundred food-bodies 

 may be seen projecting from the cushion. F. Miiller also gives 

 an interesting account of the ant army gathering its harvest ; he 

 carried home with him a branch^inhabited by a small colony, hardly 

 numbering a hundred. He removed the sheath from a pulvinus, 

 so that from fifty to a hundred fresh food-bodies were exposed. 

 The harvest was discovered almost immediately, and each ant 

 seized one of the little bodies with its mandibles and dragged it off 

 to the nest. The looser bodies were easily disposed of ; but those 

 which were somewhat more firmly attached, cost much time and 

 trouble, and were only loosened by a great deal of pulling to this 

 side and that. In ten or fifteen minutes, only four food-bodies 

 were left; and on these various ants had in vain tried their strength. 

 -Fritz Miiller supposes that the cushion protects the food-bodies 

 from drought, and from the too early visits of the ants. Is it not 

 possible that it may serve to protect the young bodies from the 

 ravages of slugs ? The most watchful ant-sentinel cannot be 

 expected to guard against the night attack of such an enemy ; but 

 the cushion of sharp hairs would certainly keep off soft-bodied 



creatures, acting in the same way as the cinders on a flower- 

 bed. 



Minute structure. — The food-bodies of Cecropia are composed 

 of a mass of cells continuous with the parenchyma of the pulvi- 

 nus and included within the epidermis. They do not include any 

 fibro-vascular bundles. The manner in which nutriment is stored 

 in the cells of the food-bodies of Cecropia is essentially the same 

 as that already described in the case of the Bull's-horn Thorn ; 

 that is to say, the cells contain a very granular protoplasm, in 

 which are embedded numerous drops of oil. I have not worked at 

 this tissue with all the same care which I gave to the study of 



