. The fungal diseases of the common larch . Larches. INTRODUCTION 13 parts of the phloem. Tetroctohedric crystals of trihydrated calcium oxalate () are occasionally present in the vacuoles of these cells (fig. 6, ). These crystals are larger than those in the small crystal-containing cells. The phloem parenchymatous elements occur more or less regularly in tangential rows, giving the effect of annual rings. Also the number of rings is approximately equal to the number of years that the stem has grown, but they are not sufficiently definite to determine an exact cor- respondence.
. The fungal diseases of the common larch . Larches. INTRODUCTION 13 parts of the phloem. Tetroctohedric crystals of trihydrated calcium oxalate () are occasionally present in the vacuoles of these cells (fig. 6, ). These crystals are larger than those in the small crystal-containing cells. The phloem parenchymatous elements occur more or less regularly in tangential rows, giving the effect of annual rings. Also the number of rings is approximately equal to the number of years that the stem has grown, but they are not sufficiently definite to determine an exact cor- respondence. (iv) Branched scleren- chymatous elements, like those in the cortex, may also be found in the outer phloem. They seem to replace elements of phloem parenchyma. (v) Medullary rays are very numerous, and may be from one to ten cells high. They are at first only one cell in thickness, but through cell divisions they may become two or more cells thick. The cells remain thin walled, and contain protoplasm and nuclei; among the contents may also be seen numerous , especially in the Adcinity of the cambium, and these drops are apparently conducted outwards to the resin sacs. The dimensions are about 5-20 n in tangential, 20 ^ in longitudinal, and 40 fx in radial direction, but the cells at the top and bottom of a ray are often extefided longitudinally. (vi) Resin cysts may also be found in the outer phloem. They have the same form as those in the pericycle, and are made by the expansion of a two-cell-thick medullary cnSc - Fig. 7.—^Transverse section of phloem ( X 420): , crystal-containing cell; , intercellular space ; , medullary ray; , pldoem parenchyma; , sieve 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 Pr
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