CHLOROPHY'CE1E (Gr. light green, and seaweed). A group of Alga which is characterized by the fact that the green chlorophyll (q.v.) of its members is not masked by other pigments. Certain Algre of a yellowish green color which were formerly considered to belong to this group have been assigned by Luther and many other systematists who follow him to a new class, the Heterokon tae. These are not only characterized by the possession of great quantities of the yellow pig ment xanthophyll, but also by the fact that they store up part of the products of their meta bolism in the form of oil, whereas it is all trans formed to starch in the true Chlorophycea.
The Chlorophycem show a remarkable di versity in form and structure. They range all the way from the unicellular Chlantydomonos and the other cilate free-swimming Volvocacete, which exhibit close affinities to the lowest forms of animal life, the Flagellate Protozoa, to the fixed many-celled filaments of Spirogyra, or the enormous complicated multinucleate cell of the Siphoned. This latter structure is unique in the vegetable world; in Caulerpa, for example, we have what is apparently a plant fully en dowed with roots, stem and leaves and several inches in length, while all that really is there is a mass of protoplasm containing many nuclei and surrounded by a single cell-wall. This structure, of course, represents not a single true cell but a mass of cells whose inner walls are undeveloped, as is evidenced by the occur rence among the Chlorophycem of forms in which the disappearance of these cell-walls or septa is only partial.
Asexual reproduction by motile spores or zoogonidia is found in most Chlorophycere, although the Conjugate never propagate them selves in this manner. Non-motile asexual spores are often found. In many of the unicel lular forms, the normal mode of reproduction is by cell division.
Sexual reproduction is found in the most varied forms. The cells which unite may be equal or unequal in size, and either motile or non-motile. In the case Spirogyra, sexual union takes place between two ordinary vegeta tive cells in place in their filaments. In a few instances, traces are found of an alternation between sexual and asexual generations.
The cells of the Chlorophycean , are all nucleate, and in almost all cases contain chloroplasts (q.v.) with pyrenoids, or masses of reserve protein. The cell-wall, though usually made up of cellulose, often exhibits the mucilag inous pectose, to which much of the slimy character of the alga in pond-scum is due.
The habitat of most Chlorophycere ,is fresh water, and most aloe- belong to the class. The majority of the Siplionea, however, and several other species of the green alga are marine. Consult Lemmerman, E., (Flagellate, Chloroptiycere, Coccosphaerales and Silicoflagellata) (Kid 1908) ; West, G. S., Treatise on the British Fresh-Water Alga) (Cambridge, Eng. 1904).