The natural history of plants, their forms, growth, reproduction, and distribution; . NANCE OF A FREE PASSAGE FOR AQUEOUS VAPOUR. aimed at is to keep a free passage for the water-vapour which must escape from thestomata. To bring this about, the stomata are situated in grooves filled with airwhich are sunk in the green tissue, and which give a striped appearance to thebranches. Water cannot force out the air from these narrow furrows which runalong the green branches and twigs, eight of them to each branch. The branches mayremain submerged in water for an hour without a trace of moisture enter
The natural history of plants, their forms, growth, reproduction, and distribution; . NANCE OF A FREE PASSAGE FOR AQUEOUS VAPOUR. aimed at is to keep a free passage for the water-vapour which must escape from thestomata. To bring this about, the stomata are situated in grooves filled with airwhich are sunk in the green tissue, and which give a striped appearance to thebranches. Water cannot force out the air from these narrow furrows which runalong the green branches and twigs, eight of them to each branch. The branches mayremain submerged in water for an hour without a trace of moisture entering thefurrow. Moreover hairs are present in the furrows as a guard against cannot be wetted, and the air adheres to them just as to the cuticular pegs ofthe bamboo leaf. A clear idea of this arrangement is given in the transversesection of the stem shown in fig. 69 ^ and 69 *. The adjacent section of the greenbranch of the Australian Casuarina quadrivalvis shows that these curious plantsalso have exactly the same arrangements, that the stomata He at the bottom of 2. Fig. 68.—Stomata iu Pit-like Depressions. Surface view of a leaf of Dryandra florihunda. A portion of the hairs which fill the pit is removed, in order to showthe stomata; x360. 2 Vertical section through a leaf of i))i/a7idm/ori6i(jirfa; x300. narrow furrows which run along the green leafless branches, and that peculiar hair-structures are present in the furrows, to which the air adheres, forming a barrieragainst water, exactly as in those of the Cytisus. The Casuaringe, which mustfinish their work for the year during the very short rainy period of their nativecountry, require during this time arrangements providing for unhindered transpira-tion no less than does the Cytisus in the Southern Alps. Altogether this con-trivance is found to be present in only a limited number of cases; in perhaps onlytwenty papilionaceous shrubs, most of which belong to the Spanish flora, of thegenera Betama, Genista,
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1902
