Plant-life, with 74 full-page illus., 24 being from photos, by the author and 50 in colour from drawings . ls which sur-vive in the struggle for existence are the best fittedto exist, and thus be the means of perpetuation of avigorous race. We have already discussed (p. 264) means of assuringa satisfactory transpiration current and devices whichprevent it being unduly checked. We have in thesame place indicated some methods of avoiding ex-cessive transpiration. The all-important stomata areusually most numerous on the. undersides of leaves,where they are variously protected lest they shouldsuf
Plant-life, with 74 full-page illus., 24 being from photos, by the author and 50 in colour from drawings . ls which sur-vive in the struggle for existence are the best fittedto exist, and thus be the means of perpetuation of avigorous race. We have already discussed (p. 264) means of assuringa satisfactory transpiration current and devices whichprevent it being unduly checked. We have in thesame place indicated some methods of avoiding ex-cessive transpiration. The all-important stomata areusually most numerous on the. undersides of leaves,where they are variously protected lest they shouldsuffer interference in the exercise of their duty. Thetender protoplasts of leaves and other green parts arescreened from excessive heat and light and fortifiedagainst rain and hail in various ways. All parts of plants are subject to the attacks offungal and bacterial fiends. Spores and germs arealmost omnipresent, floating about in the air, andseeking some weak point in a plants defences wherethey may find lodgment and flourish. They inducesome of the most devastating diseases. It so happens Plate MARSH WOUNDWORT {Stacliyi pahntris),Order LABIATJE. 1. Calyx 2. Flower, enlarged 8. Fruit DEFENCES OF PLANTS 337 that plants have developed both inward and outwardcharacters which are resistant to such attacks. Thereare certain by-products of their chemistry which havean important value in this respect. We do not ventureto assert that these by-products have been deliberatelyproduced for the purpose; on the reverse, we are dis-posed to declare that the plants which yield them chanceto have established thereby an immunity which hasbeen an important factor in their survival. Amongthese products are cork, latex, gums, resins, turpentines,ethereal oils, etc. The resin exuded from a cut madein a Pine branch is an effectual means of closing thewound and warding off bacteria. Latex is a powerfulantiseptic, a fluid of a most complex formation, generallymilky in appearance; it is developed
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1915
