. Foundations of botany. Fig. 272. —Burs. A, sticktights ; B, sticktights, two segments, magnified;C, burdock ; D, cockleburs. of stone fruits and other fleshy fruits (Sects. 242-247).Of these the great majority are eatable by man or some ofthe lower animals, and oftentimes the amount of sugarand other food material which they contain is very con-siderable. It is a well-recognized principle of botany, and 384 FOUNDATIONS OF BOTANY of zoology as well, that plants and animals do not makeunrewarded outlays for the benefit of other species. Evi-dently the pulp of fruits is not to be consumed or us
. Foundations of botany. Fig. 272. —Burs. A, sticktights ; B, sticktights, two segments, magnified;C, burdock ; D, cockleburs. of stone fruits and other fleshy fruits (Sects. 242-247).Of these the great majority are eatable by man or some ofthe lower animals, and oftentimes the amount of sugarand other food material which they contain is very con-siderable. It is a well-recognized principle of botany, and 384 FOUNDATIONS OF BOTANY of zoology as well, that plants and animals do not makeunrewarded outlays for the benefit of other species. Evi-dently the pulp of fruits is not to be consumed or used. Fig. 273. — Barbs and Hooks of Burs. I, barbed points from fruit of beggars-ticks, magnified eleven times ;n, hook of cocklebur, magnified eleven times; III, beggars-ticksfruit, natural size ; TV, cocklebur hook, natural size. as food by the plant itself or (in general) by its seeds. Itis worth while, therefore, for the student to ask himselfsome such questions as these : ^ (1) Why is the pulp of so many fruits eatable ? (2) Why are the seeds of many pulpy fruits bitter orotherwise unpleasantly flavored, as in the orange ? (3) Why are the seeds or the layers surrounding the 1 See Kerner and Olivers Natural History of Plants, Vol. II, pp. 442-i50. HOW PLANTS ARE SCATTERED ^^o^ 386 seeds of many pulpy fruits too hard to be chewed, ordigested, as in the date and the peach? (4) Why are the seeds of some pulpy fruits too smallto be easily chewed, and also indigestible, as in the figand the currant? (5) Account for the not infrequent presence of currantbushes or asparagus plants in such l
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