THE WELCOME OF THE FLOWERS 405 



marks have really been developed in correlation with the nectary. " The 

 two upper petals," he writes, " are thus marked near their bases ; and I have 

 repeatedly observed that when the flowers vary so as to become peloric or 

 regular, they lose their nectaries and at the same time the dark marks; 

 when the nectary is only partially aborted, only one of the upper petals 

 loses its mark. ... It is, however, evident that insects could discover the 

 nectar without the aid of guiding-marks. They are of service to the plant 

 only by aiding insects to visit and search a greater number of flowers within 

 a given time than would otherwise be possible; and thus there will be a 



Photo by] 



FIG. 502. BARBERRY (Berberis vulgaris). 

 The yellow flowers have irritable stamens which spring up and dust insect visitors with pollen. 



better chance of fertilization by pollen brought from a distant plant, and 

 this we know is of paramount importance." 



Hairs, prickles, the grooves of petals, and warty protuberances may also 

 serve as path-finders ; and one or more of these features may be present in a 

 flower in addition to the guiding-marks. This is the case in the beautiful 

 Orchid known as the Indian Crocus (Codogyne lagenaria, fig. 468), where the 

 yellow fringes (figs. 470, 471) borne on the lilac veins of the lip of the 

 flower, and the striped and barred markings on either side, act as path- 

 finders. At the same time, it must not be supposed that all the stripes, 

 spots, etc., of flowers are guides to the nectary. Probably in not a few 



