. The fungal diseases of the common larch . Larches. INTRODUCTION 11 formation, wliicii leaves the inner cortex intact even in old stems. Two Idnds of specialized elements occur in this layer. The first are small cells set aside for the purpose of con- taining crystals of calcium oxalate. These ceUs are only found in older stems, and are very frequent in the neighbour- hood of cankers. The second are irregularly branched sclerenchymatous cells with very thick walls (fig. 6, ). These elements grow longi- tudinally, forcing their way between the parenchymatous cells, and often branch. Th
. The fungal diseases of the common larch . Larches. INTRODUCTION 11 formation, wliicii leaves the inner cortex intact even in old stems. Two Idnds of specialized elements occur in this layer. The first are small cells set aside for the purpose of con- taining crystals of calcium oxalate. These ceUs are only found in older stems, and are very frequent in the neighbour- hood of cankers. The second are irregularly branched sclerenchymatous cells with very thick walls (fig. 6, ). These elements grow longi- tudinally, forcing their way between the parenchymatous cells, and often branch. The branching occm's when a sclerenchymatous cell en- counters a parenchymatous cell broadside, and one branch grows down on each side of the obstructing cell. The function of these cells is obscure. There is no distinction be- tween the cortex and pericycle, but in the parenchyma im- mediately abutting on the phloem (and thus presumably pericycle) there are here and . f *'• 6.—Longitudinal section of ^ •' ' phloem: , crystal-containing there large intercellular spaces cell; , medullary rav; , which contain resin. When phloem parenchyma; ; scleren- chymatous element; , sieve young they are small and tube (x 420). spherical, but with the in- creased girth of the stem they become laterally extended and are conspicuous objects in all sections; they also acquu-e a poorly developed epithelium. They appear to be associated with some of the larger medullary rays, which, when followed into the xylem, are found to be in contact with resin ducts in the first-year wood. The phloem is composed of sieve tubes, crystal-containing. 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 Hiley, W. E. (Wilfrid Edward). Oxford : Clarendon Press
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