Nature and development of plants . so placed as to afforda natural landing place for the insects visiting the flower and alsoto necessitate crossing (Fig. 290). Observe a bee visiting the DEVELOPMENT OF PLANTS 189 flowers of the carina and determine the significance of the positionand movement of the labellum and its relation to the stamen andstigma. 135. Orchidales, the Orchid Order.—The orchids are thehighest gronp of the monocotyledons and their flowers are asource of wonder and admiration, owing to the singular beautyand delicacy of their mechanical construction. Variation in thisorder has
Nature and development of plants . so placed as to afforda natural landing place for the insects visiting the flower and alsoto necessitate crossing (Fig. 290). Observe a bee visiting the DEVELOPMENT OF PLANTS 189 flowers of the carina and determine the significance of the positionand movement of the labellum and its relation to the stamen andstigma. 135. Orchidales, the Orchid Order.—The orchids are thehighest gronp of the monocotyledons and their flowers are asource of wonder and admiration, owing to the singular beautyand delicacy of their mechanical construction. Variation in thisorder has occurred on a gigantic scale, resulting in a larger num-ber of species (over 7,000) than is found in any of the precedingorders. Nevertheless these elaborate variations have not beenvery successful in enabling them to compete with other plants,and as a result the orchids are rather rare and not at all com-parable in number of individuals with the lilies and more widely distributed than anv of the other monocotv-. Fig. 291. An epiphytic orchid growing upon the branch of a tree. Thecoarse roots, r, are surrounded by a mantle of cells which take up the mois-ture from the atmosphere, b, storage organs formed from the base of theleaves, enabling the plant to produce flowers and fruit. The smaller stalks,a, are the shrivelled remains of these organs after flowering and fruiting. 39Q THE ORCHIDALES ledons, their variations have adapted them as a rule to peculiarconditions. They are especially abundant in the mountainousdistricts of the tropics, where they more commonly appear asepiphytes upon the trunks of trees and in the crevices of conditions are met by the development of a thick mantleof cells, the velamen, about the aerial roots which absorbs themoisture from the air and doubtless the enlargement of the leafbase into a bulbous storage organ enables these plants to antici-pate in this way the heavy demands that will be made upon themin the flowering se
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Keywords: ., boo, bookdecade1900, bookidnaturedevelopmen1907curt, bookyear1907
