328 REPOET UPON COTTON INSECTS. , 



This Acacia bears large paired thorns, which, "when young, are filled 

 with a sweetish pulp. Boring a hole through the wall of one of these 

 young thorns the ants eat out the contents of this one and its mate, this 

 action causing an enlargement of the thorn, so that a capacious chamber 

 is formed, and in this the ants live, remaining constantly on the tree, so 

 that Mr. Belt remarks 



I think these facts show that the ants are really kept by the Acacia as a standing 

 army, to protect its leaves from the attacks of herbivorous mammals and insects. * * * 

 I sowed the seeds of the Acacia in my garden, and reared some young plants. Ants of 

 many kinds were numerous, but none of them took to the thorns for shelter nor the 

 glands and fruit-like bodies for food ; for, as I have already mentioned, the species 

 that attend on the thorns are not found in the forest. The leaf-cutting ants attacked 

 the young plants and defoliated them ; but I have never seen any of the trees out on 

 the savannahs that are guarded by the Pseiidomyrma touched by them, and have no 

 doubt the Acacia is protected from them by its little warriors. * 



At the base of the petioles in the greater coffee- weed of the South 

 (Cassia occidentalis) are globular glands, which secrete a sufficient quan- 

 tity of nectar to render them attractive to numerous ants, wasps, and 

 bees, which would be encountered by any wingless insect in ascending 

 the stem or passing out on any leaf. Most of the upper leaves subtend- 

 ing the racemes of flowers are reduced to mere bracts, which, however, 

 have their glands large and active ; and these bear the same relation to 

 the flowers and young fruit that those lower down do to the leaves. 



Several species of Sarracenia (pitcher-plants, or trumpets) have the 

 lids or mouths of their pitcher-like leaves provided with a sweetish 

 secretion which, at certain times, in at least one species (S. variolaris), 

 extends along the margin of the wing in front of ihe leaf so as nearly or 

 quite to reach the ground. Thus a line of nectar runs from the ground 

 to and within the mouth of the pitcher, which is here provided witli a 

 flue velvety pubescence, the hairs pointing downward. Just below this 

 is a rough portion, lined with stiff bristles which also point downward. 

 The lower part of the tube, destitute of these hairs, is filled by a watery 

 liquid, Avholly or in great part secreted by the walls of the pitcher, and 

 usually protected from dilution with rain-water by the overarching lid 

 of the pitcher, the real blade of the leaf. An insect, lured up the wing 

 and to the mouth of the pitcher, while feeding on the repast so generously 

 offered, slips on the velvety surface, tries in vain to catch a firmer hold, 

 slips farther, and falls into the pitcher, whence the stiff Qhevfwx-de-frite 

 makes his escape very difficult. Reaching the water he is sooner or 

 later drowned, and being macerated there contributes to the food of the 

 plant.t 



The related Darlingtonia californica has a somewhat similarly shaped 

 leaf. Its long, twisted tube is arched above, so as to prevent the access 

 of rain-water to the secretion which fills its lower part, and the part 

 answering to the hood of Sarracenia or the blade of an ordinary leaf is 



* The Naturalist in Nicaragua, 1874, p. 219. 



tSee J. H. Mellichamp's "Notes on Sarracenia variolaris," Proc. Am. As. Adv. So., 

 xxiii, 1874, Nat. Hist., p. 113; also Riley, ibid., p. 18; and Trans. St. Louia Acad., iii, 235. 



