. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. INTERCELLULAR SECRETORY RESERVOIRS. 203 smaller than that of the neighbouring parenchyma, so that they appear very different from it in transverse sections: in rare cases they are distinguished from it by their greater width (roots of Compositae, branches of many species of Rhus according to Trecul). Their inner suiface is often slightly convex towards the passage; in the mucilage- passages of the Marattiacese it is even elongated and conical; in those of the leaves of Lycopodium the
. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. INTERCELLULAR SECRETORY RESERVOIRS. 203 smaller than that of the neighbouring parenchyma, so that they appear very different from it in transverse sections: in rare cases they are distinguished from it by their greater width (roots of Compositae, branches of many species of Rhus according to Trecul). Their inner suiface is often slightly convex towards the passage; in the mucilage- passages of the Marattiacese it is even elongated and conical; in those of the leaves of Lycopodium the cells bulge in a club-like manner. Where an epithelium can be distinguished in isodiametric cavities (Lysimachia punctata, and its ally, IMyrsine) the cells are flattened towards the surface of the cavities. The wall of the epithehal cells is delicate, in resin- and balsam-passages often coloured brown or yellow. In the mucilage-passages of old leaves of Cycas revoluta alone it is stated by Trecul' that they are strongly thickened on the side next the passage. A. Fu;. 85 —Hedera Helix ; transverse sections of the young stem (800); g resin-passages. These are in A, B, C young, and have appeared between four and five rows of cells, in the secondary cortex w b, at the limit of the zone of thickening c; It wood; in D and E older, larger passages ; b bast ^ rp parenchyma of the outer cortex. From Sachs' Textbook. There is a great lack of investigations on the protoplasm and contents of the cells of the epithelium, and of the surroundings of the secretory reservoirs generally. It seems to be certain for all cases that they contain small masses of the secretion, which then filter in some way in mass through the membrane into the reservoir. The cells surrounding the young oil passages in the roots of Compositae have clear contents, in which, in Helianthus annuus ^, large quantities of tannin are shown to be present by reagents; this is also the case with the oil in the passages. In
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