Page:Evolution of Life (Henry Cadwalader Chapman, 1873).djvu/122

88 higher plants. Botanists join, therefore, these three groups in one division, the Thallophytes or Cellular plants, a thallus being an expansion of cells.

With the Thallophytes we leave the first division of the vegetal kingdom.

The Characeae are unique plants, including the Nitella and Chara, which differ only in the structure of their tubes, the Chara having a cortical layer in addition to the simple tubes of Nitella. The Chara is found in ponds and ditches, being composed of elongated tubes giving off at intervals whorls of branches which look very much like small green candelabra. The Chara (Fig. 112) is always an object of interest to the microscopist, as exhibiting the circulation of the chlorophyll, or green matter, the globules of which may be seen ascending and descending along the sides of the tubes. The Characeae in their structure and general appearance resemble the Green Algae, while their reproductive apparatus is more like that of the Mosses. This consists of an orange-colored globule and an oval-shaped nuclule. The globule (Fig. 112, C) bursting, a number of spiral filaments come forth, which move about in the water; the nuclule (Fig. 112, D), falling off in time, gives rise to a new Chara. The globule and nuclule are supposed to be the homologues of the, reproductive organs of the higher plants. The Characeae are isolated plants, seeming to be the only remnant of a group once more numerous: they stand on a boundary-line, so to speak, separating the Green Algae from the Hepaticae. Probably extinct plants allied to the Chara gave rise to the Hepaticae, and indirectly through them to the Mosses and Ferns.