. The topography of the chlorophyll apparatus in desert plants. Chlorophyll; Desert plants; Plants. 24 TOPOGRAPHY OF CHLOROPHYLL APPARATUS IN DESERT PLANTS. distribution, but in older stems, owing- to changres in structure incident to growth and development by which the various chlorophyll-bearing- tissues are eliminated or lose their chlorophyll contents, this distribution is greatly modified. The epidermis is usually or at least frequently well supplied with chloro- phyll. This applies to stems 1 cm. or less in diameter, although a branch of P. torreyana was examined which was cm. in di
. The topography of the chlorophyll apparatus in desert plants. Chlorophyll; Desert plants; Plants. 24 TOPOGRAPHY OF CHLOROPHYLL APPARATUS IN DESERT PLANTS. distribution, but in older stems, owing- to changres in structure incident to growth and development by which the various chlorophyll-bearing- tissues are eliminated or lose their chlorophyll contents, this distribution is greatly modified. The epidermis is usually or at least frequently well supplied with chloro- phyll. This applies to stems 1 cm. or less in diameter, although a branch of P. torreyana was examined which was cm. in diameter and which, nevertheless, still had chlorophyll in the epidermis. It may be remarked in passing that this branch showed another characteristic which is unusual in Parkinsoniaâthe woody cylinder did not contain chlorophyll. As will appear later, in the ordinary se- quence of the disappearance of chlorophyll from the stem, the epi- dermis leads, followed by the pith and the wood. The most prominent mass of chlorophyll-bearing tissue in the stem, and the one that gives the color characteristic of the tree, is the outer cortical chlorophyll band. Also, this chlorophyll tissue is the most enduring. It has been iden- tified-in stems 8 cm. in diameter, and is present in the oldest parts, even in- some or perhaps most the very -base of the Fig. II.âParkinsonia torreyana: Segment of stem 7 mm. in diameter, to show the distribution of chlorophyll. Lettered as in preceding figures. instances within a few centimeters of It varies in width from 83 /«â to 246 f>- and its outer surface lies from 83 /«â to 500 /* beneath the surface of the stem. In structure the chlorophyll band is wholly of spongy tissue. The cells are cuboid and thin-walled. Within the outermost band of chlorenchyma is a ring of mechanical tissue composed of alternating groups of hard* bast and of heavy-walled paren- chyma (which later become grit-cells?). A second band of chlorenchyma lies immediat
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectplants, bookyear1908
