"Blossom Hosts and Insect Gnests 



the goal. But this last step was reserved for the 

 later seer. 



Darwin took the double problem of Sprengel, as 

 shown at E and F, Fig. 2, and by the simple draw- 

 ing of a line, as it were, as in G and H, instantly 

 reconciled all the previous perplexities and incon- 

 sistencies, thus demonstrating the fundamental plan 

 involved in floral construction to be not merely 

 "insect fertilization " of the individual flower, the 

 fatal postulate assumed by Sprengel, but "cross-fer- 

 tilization " by insects," the carrying of the pollen 

 from flower to flower, either of the same plant or of 

 different plants — a fact which, singularly enough, 

 Sprengel's own pages proved, but which he only 

 dimly suspected. Fig. 6 shows the same condition 

 as represented by G and H, Fig. 2. 



While the stigma of G is immature and cannot 

 avail itself of the pollen in its own flower, the stigma 

 of H is fully developed, while its pollen-bearing 

 anthers have withered. 



An insect — let us say Bombus — however, can 

 readily remedy this difficulty. Crawling into the 

 nectary of G, he gets himself well powdered with its 

 pollen, which he forthwith carries to the stigma of 



* Insects are by no means the only agents which nature employs 

 in this work of pollen transfer — birds, wind, and water also assist in 

 the work ; but it is with insects as the chief agents that this book is 

 concerned. 



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