Plante-vie, avec 74 illus pleine page., 24 étant de photos, par l'auteur et 50 en couleur des dessins . dents des phénoménales une fois précipité à la conclusion que l'auto-fécondation était un vrai mal. Mais cette notion est maintenant en cours de révision. Cette fécondation croisée a ses avantages ne sera pas niée, mais ils ne sont pas faciles à définir. D'autre part, il n'est pas démontrable de la thatésauto-fécondation dans les fleurs, où il se produit, a un effet anynocif sur leur postérité; en effet, certaines des mauvaises herbes généralisées et énergiques, y compris les espèces suchnoconnues comme les Shepherds-Purs

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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 LVI.. 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 suffer.Cross-breeding

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• bookcentury1900
• bookdecade1910
• booksubjectbotany
• bookyear1915