THE AMERICAN BOTANIST. 49 



thus the nectary would become an object for selection. 

 He cites the case of the leaves of certain trees where a sac- 

 charine fluid, often called honey-dew, is excreted without 

 the aid of special glands. B\^ some, the special use of 

 extra-floral nectar is supposed to be to divert ants and 

 other insects from visiting flowers which they might 

 otherwise injure. But many plants have nectar long be- 

 fore and long after the flowering period. On Viburnum 

 opulus, for example, nectar is still present and abundantly 

 used b^^ ants late in October. Another view has been that 

 certain of these glands act as absorptive cups and surfaces 

 for the absorption of rain and dew. In Euphorbia pul- 

 cherrima, commonly cultivated in green houses, there are 

 very large cup-shaped nectar glands, one on the involucre 

 of each cyathium. There are also stipular glands and 

 glands on top of the petiole at the base of the blade. Ants 

 visit the large glands very extensively and one might be 

 inclined to believe that in such cases the foliar glands are 

 guides to the more abundant sweets to be found higher up 

 when the plant is in bloom. In the case of submerged 

 water plants, as for example in certain species of Potamo- 

 geton with glands on the leaves, the entire question of a 

 relationship between insects and glands in general is 

 eliminated. 



Besides nectar there are various other secretions ; im- 

 portant among which are those with a digestive function 

 and those of a sticky nature to prevent crawling insects 

 from passing certain parts or for holding them fast w^hile 

 they die and decay. 



During the past summer, the writer spent some time in 

 studying the glands which appear on the blades, petioles, 

 stipules and other parts of our native and cultivated 

 plants. The mode of occurrence and the character of these 

 organs is quite erratic. A species may have highly devel- 

 oped glands while its near relatives have none whatever. 

 Even on a given individual some leaves may have the 

 glands while others have none and rarely is the number 

 constant. 



