Plant-life, with 74 full-page illus., 24 being from photos, by the author and 50 in colour from drawings . dents of the phenomenaat one time rushed to the conclusion that self-fertiliza-tion was an actual evil. But that notion is now under-going revision. That cross-fertilization has its ownadvantages will not be denied, but they are not easy todefine. On the other hand, it is not demonstrable thatself-fertilization in flowers, where it occurs, has anyharmful effect on their posterity; indeed, some of themost widespread and vigorous weeds, including suchwell-known species as the Shepherds-Purs
Plant-life, with 74 full-page illus., 24 being from photos, by the author and 50 in colour from drawings . dents of the phenomenaat one time rushed to the conclusion that self-fertiliza-tion was an actual evil. But that notion is now under-going revision. That cross-fertilization has its ownadvantages will not be denied, but they are not easy todefine. On the other hand, it is not demonstrable thatself-fertilization in flowers, where it occurs, has anyharmful effect on their posterity; indeed, some of themost widespread and vigorous weeds, including suchwell-known species as the Shepherds-Purse (GapsellaBursa-pastoris), the Groundsel {Senecio vulgaris), andChickweed {Stellaria media), are self-fertilized. It isobvious that self-fertilization can take place only inhermaphrodite flowers—that is, in those which includein the same flower both male and female organs. Thegreat Linnseus tumbled to the conclusion that her-maphrodite flowers were invariably self-fertilized. Heevidently had not time to observe the varied devices insuch flowers for the avoidance of self-fertilization. We Plate GROUND IVY (Nepeta gUchoma),Order LABIA7EJE. POLLINATION 303 now know that cross-fertilization is exceedingly com-mon among hermaphrodites, but we have also learnedthat, wonderful as are the devices in many such flowerswhich have relation to cross-fertilization, in the sameflowers there are devices, not one whit less wonderful,by which self-fertilization is achieved, either in supple-ment to cross-fertilization, or to ensure the formation offertile seed in the event of its failure. Cross-fertiliza-tion is so widespread that it must have an importantsignificance, for in Nature nothing walks with aimlessfeet. Probably its essential purpose is the maintenanceof a high standard in the race by avoiding degenera-tion due to inbreeding. Contrary to common thought,inbreeding is not disastrous if the parents are healthy;but if parents are not sound, the progeny must
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1915
