NECTAR GLANDS. 85 



distant part of his plantation he observed a large number of moths fly- 

 ing about some cow-pea vines that were growing in a corn-field. I at 

 once equipped myself with a lantern and proceeded to the corn-field. On 

 arriving there I witnessed a remarkable sight ; thousands of the cotton- 

 moths were about the pea- vines feeding on the nectar excreted by a 

 series of glands situated near the end of the peduncle which is produced 

 beyond the last flower or pod. The moths were not at all shy, but 

 would remain engrossed in partaking of their repast even when the 

 lantern was brought within a few inches of them. In no instance were 

 the moths seen to visit the flower of the pea. 



It is probable that the cotton-moth feeds about nectar excreted by 

 many other plants. Mr. Trelease observed it feeding at the ovate glands 

 which are situated at the base of the petiole of the larger coffee weed 

 (Cassia ocmdentalis). 



The subject of extra floral nectar glands is very interesting; and it is 

 one which has been studied but little. The problems presented by it 

 are quite puzzling. In the case of the nectar glands of flowers we have 

 organs which, serving to attract bees and other insects, and thus in- 

 suring cross-fertilization, are very useful to the plant. But the functions 

 which extra floral nectar glands perform are seldom as obvious. In case 

 of the cotton plant these glands serve to attract the moths and thus 

 insure the ovipositiou of eggs upon it. Thus the plant upon which the 

 glands are the most active will prove most attractive to the moths, and 

 hence will be the one the most likely to be infested by worms. There- 

 fore, instead of being beneficial, as we know the floral nectar-glands to 

 be, the extra floral glands seem at first sight to be injurious to the 

 plant. 



It was not until we learned that the small ants, so abundant in cotton 

 fields and which are attracted to the plants by these glands, are the most 

 efficient check upon the increase of cotton-worms that we understood 

 how beneficial these glands really are. For, although the moths, led by 

 instinct to oviposit only upon the food plant of their young, would 

 visit the cotton plants even if the glands were not present, it is not im- 

 probable that the ants are first attracted to the plants by the supply of 

 nectar which they find there, and as this nectar is secreted by the very 

 young plants the ants doubtless begin the 'destruction of cotton-worms 

 as soon as they appear. The statement of Professor Eiley that \ k these 

 sweets are first produced when the plant begins to flower and fruit" 

 (Annual Report Department of Agriculture, 1878, p. 215), was merely a 

 conjecture which subsequent observations failed to confirm. In reality, 

 glands were found on some cotyledons ; these, however, did not seem to 

 secrete nectar; but the gland on the first leaf begins to secrete nectar 

 (as indicated by the first visits of ants) about the time that the third or 

 fourth leaf expands.* 



"The bearing of this subject of nectar upon the subject of the enemies of the cotton- 

 plant is so important that \ve have requested Mr. Trelease to prepare a paper upon it, 

 which will be found in Part III. 



