Ch. VI, 5] METHODS OF CROSS-POLLINATION 



293 



Not only does the structure of the typical showy flower 

 exhibit remarlvable fitness to cross-poUination by insects, 

 but this fitness is carried to degrees which have evoked the 

 wonder and admiration of long generations of loving ob- 

 servers of plants. The simplest condition is found in regular 

 flowers like Buttercups or Apple Ijlossoms, where almost 

 any kind of insect may equall}- well ahght in the shallow 

 basin, and, busily seeking the /,? 



nectar, effect pollination. This 

 is likewise the case with the 

 Compositte, — the Dandelions and 

 Daisies and Sunflowers, and that 

 sort. In irregular flowers, such 

 as the Larkspur and Mints (Fig. 

 203), the arrangements are such 

 that only Bees and like insects 

 can reach the nectar in the elon- 

 gated spurs or tubes ; and those 

 are the principal insects which 

 visit such flowers. In these 

 flowers, as elsewhere, the me- 

 chanical arrangements are such 

 that the visiting insect must take 

 a path which insures cross-pol- 

 lination. In some Orchids, espe- 

 cially the Lady's Slipper (Fig.204), 

 the insect has to enter the flower 

 b}' one opening which the stigma guards, and leave b}' another 

 over which hangs an anther. In Orchids, indeed, the fitting 

 of floral form to insect shape and habit has become wonder- 

 fullj' exact, so that in some cases only a single species of 

 insect can pollinate the flower, the adjustment between the 

 two being carried remarkabh' into details. These, how- 

 ever, are but few of the great ^'ariety of arrangements pre- 

 sented in this relation between flowers and insects, which 

 include even a case of deliberate and purposeful pollination 



Fig. 205. — A flower of Yucca 

 Whipplei, being pollinated by a 

 Pronuba moth; X y- 



The insect deliberately col- 

 lects pollen from one flower, car- 

 ries it to the stigma of another, 

 and there presses it securely 

 down. It then lays an egg in 

 the ovan,' of that flower, and its 

 lar\'a feeds on some of the seeds, 

 which would not develop without 

 the pollination. (From Kerner, 

 after work by Trelease.) 



