divided by transverse walls into a single row of several cells, three or four of the terminal of which are then divided by median longitudinal walls. This divided terminal portion by growth and multiplication of its cells becomes ovate or spatulate in outline. In the latest stage that we have been able to see, one somewhat more advanced than that represented in our f. 21, the whole body still consists of only one layer of cells. F. 22 shows in edgewise view the same plant that is shown in f. 21. A root-hair is sent out from the spore soon after the emergence of the germ-tubes.
A second species of Riella, apparently new, from the Canary Islands, has come to our attention; this we would describe as follows:
Riella affinis sp. nov.
Apparently erect or ascending, becoming prostrate on the subsidence of the water, 6–15 mm. high, densely caespitose, simple or sparingly furcate: axis flattened, 0.1–0.4 mm. wide, mostly thin and flaccid, radicelliferous at base: wing 1–3 mm. broad, rounded or obtusely pointed at apex and falciform, deeply lobed; cells near the axis 45–60 μ in diameter, those near the margin about 30 μ: scales usually inconspicuous, 0.2–0.5 mm. long, linguiform, lanceolate, or linear, obtuse or acute: monoicous: antheridia solitary or in groups of 2–7 in more or less profound marginal sinuses: sporogonia mostly 3–10: involucres ovoid, 8-winged, 1.4–2 mm. long, 1–1.5 mm. wide (incl. wings), much contracted and often subacute at mouth; wings 0.1–0.2 mm. broad, with undulate-sinuate or subentire margin: capsule subglobose, 0.8–1 mm. in diameter, seta 0.1–0.2 mm. long: spores brown, 85–120 μ in maximum diameter (spines included); outer face densely covered with spines 6–15 μ long, their apices mostly truncate, often slightly dilated, occasionally emarginate-bifid, rarely acute, the supporting basal membranes sometimes almost deficient but commonly forming a few imperfect areolae; inner faces with mostly truncate or obtuse spines or warts 3–6 μ high, basal membranes wanting. (Pl. 12. f. 23–36.)
On the bank of a reservoir, Tafira, Grand Canary, June, 1897, O. F. Cook (no. 729). We are informed by the collector that the specimens were found partly submerged and partly exposed on a sloping bank.
Riella affinis is allied to the Algerian R. Cossoniana Trabut and the central Asian R. Paulsenii Porsild, but differs from both in being monoicous and in the much longer spines of the larger
