. Botany of the living plant. Botany; Plants. MODIFICATIONS OF FORM 201 {decussate arrangement). This arrangement may be maintained through life, as it is in the Dead-Nettie, Willow-herb (Fig. 133), Lilac, Horse-Chestnut, or Sycamore. The upright shoot of the Sycamore is a good example of the way in which the circular area round the axis is put to the best use by leaves arranged on a decussate plan. Each successive pair fits into the gap between those of the preceding pair. But if the internodes were short, as they are in the young state, the higher would overshadow the next pair but one of lo
. Botany of the living plant. Botany; Plants. MODIFICATIONS OF FORM 201 {decussate arrangement). This arrangement may be maintained through life, as it is in the Dead-Nettie, Willow-herb (Fig. 133), Lilac, Horse-Chestnut, or Sycamore. The upright shoot of the Sycamore is a good example of the way in which the circular area round the axis is put to the best use by leaves arranged on a decussate plan. Each successive pair fits into the gap between those of the preceding pair. But if the internodes were short, as they are in the young state, the higher would overshadow the next pair but one of lower leaves. This difficulty is met by the lower pair having longer petioles, so that. Fig. 134. Young leafy shoot of Sycamore seen from above : showing how with very little overlapping the leaf-blades form a mosaic. The spaces unoccupied centrally will be filled as the younger leaves expand. their blades are carried out beyond those of the leaves immediately above them, forming a compact " leaf-mosaic " (Fig. 134). The decussate is the simplest of the cyclic or whorled arrangements, where two or more leaves are seated at the same level. But in other cases the number of the leaves at the same level may be not two only, but three, four, or more. As in the decussate plan the leaves of each succeeding whorl alternate as a rule with those of the preceding, so that they occupy the spaces between them, an arrange- ment that is very convenient in the packing of the crowded parts into small compass in the bud. A transition to higher numbers in the cycle may be seen in the individual plant. Thus in Fuchsia, which has usually decussate leaves, a very strong shoot may bear alternating whorls of three. In Lysimachia vulgaris, and in the Privet, a like. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Bower, F. O
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