June, 1907 



AMERICAN HOMES 



AND GARDENS 



215 



tLires is better fitted for the task. Many kinds of insects 

 spend practically their whole lives in passing from one flower 

 to another. The hairs with which the bodies of many are 

 covered are well adapted for collecting and retaining the 

 pollen-dust. Finally, many insects have a habit of visiting 

 diflerent individuals of one kind of flower in succession, even 

 to the extent of neglecting the showy blooms of other species 

 which may come in their way. 



In all likelihood, insects first began to visit flowers as mere 

 robbers. That is to say, they came to eat the pollen. This 

 may have been at a period so remote, geologically speaking, 

 that flowers as we know them, with brightly colored petals, 

 may not have existed. Some of these grains chance-collected 

 on their bodies, the insects would almost certainly deposit 

 upon the pistil of the next bloom visited; and if this bloom 

 happened to belong to the same species as that from which 

 the pollen was carried, cross-fertilization would be effected. 

 Thus, these chance transfers of pollen from one bloom to 

 another would benefit the plants concerned, and by the law 

 of natural selection, chance would tend to strengthen into 

 certainty. 



Through what stages this wonderful evolutionary process 

 passed it is not possible to say with exactness. The secre- 

 tion by the plant of nectar, or honey, marked a definite step 

 in advance. The sweet liquid constituted a counter-attrac- 

 tion to the insects, which thus devoured less of the valuable 

 pollen, albeit they did not carry away less of it on 

 their bodies. Indeed, at the present day, many kinds of in- 

 sects visit flowers for honey alone and never eat pollen. Thus, 

 the flowers have, in effect, changed the tastes of their insect 

 visitors in order to promote their own ends. 



Another great step in advance was the production by in- 

 sect-fertilized flowers of brightly colored petals. These 

 showy banners act, as it were, as advertisements. They say 

 to the insects: "Here is nectar; come and sip my sweets." 

 Moreover, they doubtless constitute a time-saving device, 

 rendering the flowers more easy of discovery by the insects, 

 Also, they form a ready distinction between flowers of dif- 

 ferent species; and this is Important, as it is obviously neces- 

 sary, if cross-fertilization is to be secured, for the pollen from 

 one flower to be transferred to another of the same kind. 

 It has already been said that many insects systematically 

 visit the flowers of one species to the exclusion of others 

 from their "visiting list." 



We have now, therefore, formed a definite idea of the 

 manner in which flowers are aided by their insect visitors, 

 and of how these visitors are encouraged and entertained. 

 But we are really only on the outskirts of a very wide and 

 a very wonderful subject. There is, of course, a more or less 

 haphazard cross-fertilization of flowers by insect agency. 

 Thus, butterflies often visit flowers to suck the nectar, and 

 carry away with them a quantity of pollen on head and 

 thorax. Many butterflies prefer certain kinds of flowers to 

 others. "Peacock" butterflies (Fig. 2), for example, love 

 especially the various scabious blooms and their allies. Again, 

 one often sees certain flowers crowded by small beetles, the 

 insects being at times almost smothered in the pollen (Fig. 

 3) . This Is especially the case at certain seasons of the year, 

 with the large, flat heads of umbelliferous blooms. As the 

 insects fly constantly from one flower head to another, they 

 transfer quantities of pollen. 



But observation has proved that certain flowers are espe- 

 cially modified In anticipation of the visits of special kinds 

 of insects, and that these modifications have, in not a few 

 Instances, been developed to an extraordinary extent. There- 

 fore, If we wish to form a correct mind-picture of the nup- 

 tials of the flowers, we must examine at least a few of these 

 special cases. We may begin with what has been aptly 

 termed the "brush and piston mechanism," as seen in the 

 cultivated pea and allied blooms. Consideration of space 



4 — Diagrams Showing the Percussive Mechanism of the Sage Bloom 



1 



5 — Honeysuckle Visited by Dusk-flying Hawk Moth 



6 — Tobacco Flowers Visited by Very Long-tongued Moth, a Well 

 Known Central American Species Known as 

 Phlegethontius Nosticus 



