172 AMERICAN HONEY PLANTS 



they not time the maturity of these essential parts so as to secure effective 

 functioning without all the nectar machinery? In other words, why is 

 crossing so commonly necessitated and provided for? 



Science of every kind has been advanced by three methods — reason- 

 ing, observation, experimentation. Sprengel's answer was reached by the 

 first two; the new answer sought by Darwin was to be obtained through 

 the third. For eleven years he put the question direct to the plants them- 

 selves, fertilizing them by their own pollen, crossing them, raising and 

 requestioning their offspring. More and stronger progeny from crossing 

 was the answer. 



The popularity that Linnaeus had given to characterizing and classi- 

 fying living things, was transferred by Darwin to studying their structure 

 and doings. Sprengel's idea fell upon barren soil; Darwin's was cultivated 

 with care and skill. 



Two men — Mueller, a German, and Delpino, an Italian, stand out most 

 prominently among a multitude who observed and wrote and pictured the 

 marvels of flower and insect harmonies for a generation. All did excellent 

 work in furnishing details and corroborations; but Darwin had answered 

 the question as to the what and the why of the nectar of flowers. 



But there is nectar that is not produced in flowers. Look at the queer 

 spots in the angles between the veins on the under side of a catalpa leaf, 

 when it is young; or at the little goblets on the stalk of a cherry or peach 

 or snowball leaf, or at the pin-head spots on a trumpet-creeper or paeony 

 calyx, and you may see glands there that secrete a sweet fluid. Bees may 

 not care for it, but wasps or ants do. The cotton plant has such sweet nec- 

 tar glands on the outside of the cluster of bracts about each blossom, and 

 on the back of its leaves. 



in a very few cases such "extrafloral" nectar serves the same purpose 

 as that within the flowers ; but generally it does not lead to fertilization. 

 Delpino called the nectar that leads to fertilization "nuptial" nectar, and 

 the other "extranuptial." 



In the seventies of the last century an English mining engineer, Belt, 

 well known in the ore regions of Colorado, was marooned by his profes- 

 sion on a mining property in Nicaragua. Using his eyes took the place 

 with him of tennis, or of dissipation, which is the white man's bane in the 

 tropics. He saw that a certain kind of ants cut the leaves of trees into 

 bits which they take into their nests, and that roses and other introduced 

 plants fared hard with these leaf cutters, unless they were protected by 

 aromatic oils, as various kinds of citrus leaves are, or in some other way. 



Belt did not fail to notice that ants visited extrafloral nectaries in 

 numbers. In the case of those on some acacias he found the ants very 

 pugnacious. I confess that in Guatemala I have preferred, myself, to go 

 around a bush or a grove of such acacias with their ant guards. As with 

 Sprengel's geranium hairs, these nectaries unfolded question after ques- 

 tion. 



In Belt's case, the tips of the acacia leaflets ripen also into little fruit- 

 like bodies that the ants gather and take into their nests; and they 



