. Outlines of botany for the high school laboratory and classroom (based on Gray's Lessons in botany) Prepared at the request of the Botanical Dept. of Harvard University. Botany; Botany. 76 THE LEAF " Sleep of Plants" to all such movements from the evident suggestion of rest. A definite advantage is gained by the nocturnal position. The surfaces of the blades being vertical, or nearly so, and the several leaflets brought to- gether in a cluster (in the case of compound leaves), there is less likelihood that the leaves will be chilled or, in cool climates, frost-bitten. 118. The &quo
. Outlines of botany for the high school laboratory and classroom (based on Gray's Lessons in botany) Prepared at the request of the Botanical Dept. of Harvard University. Botany; Botany. 76 THE LEAF " Sleep of Plants" to all such movements from the evident suggestion of rest. A definite advantage is gained by the nocturnal position. The surfaces of the blades being vertical, or nearly so, and the several leaflets brought to- gether in a cluster (in the case of compound leaves), there is less likelihood that the leaves will be chilled or, in cool climates, frost-bitten. 118. The "Sensitive ; â The most striking exhibition of leaf movements after stimulation is perhaps given by the house plant, known from its peculiar behavior as the Sensitive Plant (Mhnosd puilica). The merest touch on one of tlie leaflets causes the suc- cessive closing togetlier of all the neighboring leaflets, or perhaps all parts of the entire leaf. If tlie shock is slightlj' increased, the effect may not only traverse the entire leaf and cause it to droop on the stem, but lie transmitted to tlie other leaves as well.^ 119. Leaves without blades. â In a few cases the blade of the leaf is quite lacking, while its place is supplied by the enlarged and flat- tened petiole. Certain Acacias of Australia normally have no oth n- foliage. In the seedling, however, leaves appear bearing blades. As the seedling grows older, the petioles of these bladed leaves are seen to be flat- tened. Finally the blades fail altogether, on leaves produced at a little later Terminal pmlion ,,f the shnot of a seed- stage, only/)/('/«o(/«.5 (phyl- lint; Araeia: 1, llie last of tlie seodlincr , ,â \ ' â¢' ,r^. r-r^s 1 . 1 . 11 J o 1 .? iO'/((T) appearinu'(r Iff. 60). leaves to siiow true blades; 2 and o, y it oV o -'"J' bladeless, flattened petioles, or phyl- The flattening is vertical, lodes. so that the phyllode (phi/l- lodinm) presents its edges to earth and sky. This fact, even
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