The natural history of plants, their forms, growth, reproduction, and distribution; . water. If now the leaves be completely submerged,the silver lustre is only shown on those parts which were not previously immersed,and where water could not replace the exhausted air;—the spaces round the pegsin this region having been again supplied with air on the opening of the stop-cockof the pump in order to submerge the leaves. It may be imagined from thisexperiment how much the stomata would be damaged by water if the plantsmentioned were not protected from moisture by the pegs to which the air adheres
The natural history of plants, their forms, growth, reproduction, and distribution; . water. If now the leaves be completely submerged,the silver lustre is only shown on those parts which were not previously immersed,and where water could not replace the exhausted air;—the spaces round the pegsin this region having been again supplied with air on the opening of the stop-cockof the pump in order to submerge the leaves. It may be imagined from thisexperiment how much the stomata would be damaged by water if the plantsmentioned were not protected from moisture by the pegs to which the air adheresso strongly. In many plants which grow in the sunshine, and particularly in those whosefoliage is evergreen and only exposed to moisture at the time of the greatestactivity of the sap (while later it is exposed for months to dry air), the stomata areto be found surrounded by an embankment, or sunk in special pits and in the leaves of many indigenous plants, which are green in the summer, those of the Carrot (Daucus Carota), the guard-cells of the stomata are so. 296 MAINTENANCE OF A FREE PASSAGE FOR AQUEOUS VAPOUR. over-arched by the neighbouring epidermal cells that a sort of vestibule is formedin front of the true pore. It can easily be imagined that drops of water whichcome to such places are not able to press out the air from this vestibule, and there-fore cannot penetrate to the guard-cells of the stomata. In Hakea Jiorida andProtea Tnellifera, two Australian shrubs (see fig. 67), similar arrangements are metwith, but here the stomata are still more over-arched, so that they are only visibleto anyone looking at the surface of the leaf through small holes at the top of thedome. The stomata on the green branches of various species of Ephedra aresurrounded by mound-like projections from the cuticle of neighbouring epidermalcells, and are at the same time somewhat sunken, so that an urn-shaped space is i,-1,r-v-r^~r-l,^ ^
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1902
