NECTAR AND ITS USES. 321 



them. Floral glands may occur as modifications or appendages of any 

 of the floral organs ; extra-floral glands may occur as modifications or 

 appendages of the outer floral envelope, or of various extra floral organs, 

 as shown in the following table : 



Eeceptacle. 



Pistil. 

 Floral Stamens. 



Corolla. 



Calyx. 



Calyx. 



Ordinary bracts. 



Specialized bracts. 

 Extrafloral. Involucre . 



| Peduncle. 

 [Leaf. 



The secretion of glands of the first group seems always designed to 

 aid in the fertilization of the flowers in which it is produced by attract- 

 ing to them insects or birds, which, by reason of some floral adaptation, 

 while feeding on the nectar, or on small insects likewise attracted to it, 

 unconsciously transfer pollen from the anthers to the stigma of this or 

 some other flower of the same species. Some of these flowers are of an 

 open structure, with their nectar accessible to insects of all sorts and 

 sizes; others are of such size and form as to be limited to certain groups 

 of insects, sometimes even so restricted as genera. Some are so formed 

 that fertilization is possible by direct pollination without extraneous 

 aid; others never produce offspring unless they receive such aid. So 

 much has been written concerning floral nectar and its uses that I shall 

 give but one example under this head, the flower of the cotton plant. 



The cotton flower is very fugacious ; opening shortly after sunrise, it 

 has passed its prime before sunset, and by the end of the second day 

 the corolla and stamens have usually fallen to the grcrand.* 



* As is well known, the corolla of one of these flowers is creamy white on opening ; 

 later in the same day it becomes more or less tinged with pink or rose, which becomes 

 a uniform deep rose on the second day. As will presently be shown, these flowers are 

 not dependent on insect aid for their fertilization, yet the great size and conspicuous 

 color of their corolla indicates to the believer in the commonly accepted theory of the 

 evolution of floral forms that this has not always been the case; in other words, that 

 there was a time when, for some purpose, they needed to attract insects or other 

 animals, to which their showy corollas rendered them visible from a distance. But 

 why should the color change so markedly as the flower advances in age? There is 

 reason for believing that fertilization occurs during the first day of blooming, and 

 this being the case insects are not needed by any flower more than one day old. Many 

 other cases could be given where the color of a corolla changes and becomes intensified 

 after the fertilization of the flower to which it belongs, but it is unnecessary to more 

 than mention them here. The most satisfactory explanation of this phenomenon that 

 is known to me is that by their varied, lasting, and augmented coloration they attract 

 flower-haunting animals to the plant. These instinctively, or by experience, visit 

 only the younger flowers, readily distinguishable by their color from the older ones. 

 See Nature, ix, 460, 484 ; x, 5 ; xvii, 78 ; and Delpiuo, Ult. Oss., 1875, p. 28. 

 21 c I 



