. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. ^54 PRIMARF ARRANGEMENT OF TISSUES. rather spring from them: tlie same is the case with those of the lowest internode of a branch, so that the latter are not in direct continuity with those of the stem (Reichardt). The occurrence of medullary bundles is a purely specific property. Of eight investigated species of Peucedanum they appear only in P. Oreoselinum: they are absent in Silaus tenuifolius. They are not present in the one-year-old seedling of S. pratensis. Some Ma»iUlarias ^ h
. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. ^54 PRIMARF ARRANGEMENT OF TISSUES. rather spring from them: tlie same is the case with those of the lowest internode of a branch, so that the latter are not in direct continuity with those of the stem (Reichardt). The occurrence of medullary bundles is a purely specific property. Of eight investigated species of Peucedanum they appear only in P. Oreoselinum: they are absent in Silaus tenuifolius. They are not present in the one-year-old seedling of S. pratensis. Some Ma»iUlarias ^ have, within the typical ring of bundles of the leaf-trace, a second in the peripheral parts of the pith, this being composed of numerous small cauline bundles, la INI. angularis, and an undetermined similar species, there are about thirty of th-ese. They ascend the stem parallel to those of the leaf-trace, are strongly undulated in a radial, and especially in a tangential direction, and anastomose at acute angles. They are absent in young seedlings and in young shoots, and appear later at some height above the base of the shoot, springing from the inner side of the bundles of the trace. I was unable to find anastomoses with the leaf-trace, or the ring of secondary wood, excepting at their point of origin. In other INIamillarias, as M. pusilla, glochidiata, &c., I looked in vain for the medullary bundles, even in the mature shoot. Of other Cactaceae, forms of Echinocactus and thick ones of Cereus ( C, candicans?) have a medullary system of bundles, which on account of its peculiar relation to the lateral shoots will be described in Sect. 94. The small Orobancbex have in their stems only the typical Dicotyledonous ring of vascular bundles. Strong stems of the more robust forms, as O. elatior Sutt., rubens Wallr., caryophyllacea Sm., Rapum Thuill., and Cistanche lutea'^, have, inside the ring, and scattered in the pith, small bundles, the number of which is variable, and
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