. Carnegie Institution of Washington publication. STRUCTURE. 43 12, 13, 14, f, 15, 1 6, 17, f, 18, 19, 20, f, 21, 22, 23, f, 24, 25, 26, f, &c; the primary spiral seemed to be sometimes ^T, sometimes higher. N. rubra in the Munich garden (which Raciborski considered was more probably a hybrid) showed i, 2, f, 3, 4, 5, 6, f, 7, 8, f, 9, 10, n, 12, f, 13, 14, 15, 16, f, 17, 1 8, f, 19, 20, 21, 22, f, 23, 24, 25, 26, f, 27, 28, f, 29, 30, 31, 32, f, 33, 34, 35, 36, f, 37, 38, f, 39, 40, 41, 42, f, 43, 44, 45. 46, f, 47. 48, f, 49. 50, 51- 52, f, 53- 54, 55- 56, f. 57, 58, f, 59, 60, 61, 62, f
. Carnegie Institution of Washington publication. STRUCTURE. 43 12, 13, 14, f, 15, 1 6, 17, f, 18, 19, 20, f, 21, 22, 23, f, 24, 25, 26, f, &c; the primary spiral seemed to be sometimes ^T, sometimes higher. N. rubra in the Munich garden (which Raciborski considered was more probably a hybrid) showed i, 2, f, 3, 4, 5, 6, f, 7, 8, f, 9, 10, n, 12, f, 13, 14, 15, 16, f, 17, 1 8, f, 19, 20, 21, 22, f, 23, 24, 25, 26, f, 27, 28, f, 29, 30, 31, 32, f, 33, 34, 35, 36, f, 37, 38, f, 39, 40, 41, 42, f, 43, 44, 45. 46, f, 47. 48, f, 49. 50, 51- 52, f, 53- 54, 55- 56, f. 57, 58, f, 59, 60, 61, 62, f, &c.' The structure of the stem in Nymphaeaceae has long been a puzzle, and for the most part still remains so. A transverse section of any vegetative stem of Nymphaea (Fig. 16) shows to the unaided eye three well-marked regions, viz., (i) an outer wall of dense cellular tissue, about o. 16 cm. thick, consisting of epidermis and exo-cortex, (2) a medio-cortex full of large lacunee or air-spaces, (3) a dense central core traversed in every direction by vascular bundles. The second layer is traversed by numerous trabeculae of denser tissue connecting the exo-cortex with the central core. The following description applies only to normal vegetative stems, not to stolons or resting tubers. Microscopically examined, a well-marked epi- dermis is always present. In N. lotus and odorata /T7- _\ .1 • • -11 111 FIG. 16.— Rhizome of J\T. odor- (rig. 17) this is an irregular layer as to the level aia- transverse section ot in- of the cells on the outer and inner sides, and as. to their size, though they are approximately cubical heavy llnes are v«scular bun- ' , , , . ,, • , dles- Natural size, in shape. 1 he walls are equally thin on all sides. In N. flava the cells are much shallower than long or broad (about 2:1) and form a more even surface. With the exception of a very minute area at the growing point of the stem, its whole surface is covered with hairs. Where these first
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