Flowers. 181 



like outgrowths from the two lower stamens secrete the 

 nectar and pour it into a cup formed by the base of the 

 lower petal. 



The nectaries may occur on any part of the flower, but 

 they are most frequently found at the bases of the stamens, 

 petals, and ovaries, and rarely on the calyx. In the plum 

 and peach they form a thick inner lining of the cup-shaped 

 receptacle. In Nasturtiums the nectar is secreted in a 

 long spur from the calyx. 



Some flowers of simple construction expose their nectar 

 freely to all sorts of insects, but others conceal it in various 

 ways so that it is accessible only to insects of certain kinds. 

 A frequent device is to have some parts of the corolla close 

 over the way to the nectar so that small insects which 

 would not assist in cross pollination are excluded, and only 

 those which are strong enough to push aside the barrier 

 or have proboscides of proper construction to thrust past 

 it can obtain the nectar and accomplish the transference 

 of the pollen. 



The student is quite certain to find that irregularities and 

 complexities of floral structure are in the interest of the 

 protection of the nectar or pollen and the transference 

 of the latter from one flower to another. 



132. Color and Fragrance. As Sprengel pointed out, 

 flowers not only provide food for insects, but they also 

 furnish advertisements in the way of brilliant colors and 

 agreeable odors to notify insects from afar where food 

 awaits them, and lines, spots, etc., of special color to show 

 insects coming to the flowers the direct way to the nectar. 

 It appears from various experiments that the odor is most 

 effective in attracting insects from a considerable distance, 

 and that on the nearer approach of the insect the color be- 

 comes an important guide. There seems to be no doubt 



