385. Order Cryptonemiales.—Examples are Dudresnaya, Melobesia, Corallina, etc., the last two genera include many species with a wide distribution.
Class Charophyceæ,
Order Charales.
386. The Charales are by some thought to represent a distinct class of algæ standing near the mosses, perhaps, because of the biciliate character of the spermatozoids. There is one family, the Characeæ. The plants occur in fresh and brackish water. Aside from the peculiarity of the reproductive organs they are remarkable for the large size of the cells of the internodes and of the “leaves,” and the protoplasm exhibits to a remarkable degree the phenomenon of “cyclosis” ([see paragraphs 17-20]). Three of the genera are found in North America (Chara, Nitella ([Fig. 8]) and Tolypella).
Fig. 172a.
Reproductive organs of Chara fragilis. A, a central portion of a leaf, b, with an antheridium, a, and a carpogonium, s, surrounded by the spirally twisted enveloping cells; c, crown of five cells at apex; β, sterile lateral leaflets; β′, large lateral leaflet near the fruit; β″, bracteoles springing from the basal node of the reproductive organs. B, a young antheridium, a, and a young carpogonium, sk; w, nodal cell of leaf; u, intermediate cell between w and the basal-node cell of the antheridium; l, cavity of the internode of the leaf; br, cortical cells of the leaf. A × about 33; B × 240. (After Sachs.)
386a. The complicated structure of the sexual organs shows a higher state of organization than any of the other living algæ known. While the internodes in Nitella are composed of a single, stout cell, some times a foot or more in length, the nodes in all are composed of a group of smaller cells. From the lateral cells of this group lateral axes (sometimes called leaves) arise in whorls.
In Nitella the internodes are naked, but in most species of Chara they are corticated, i.e., they are covered by a layer of numerous elongated cells which grow downward from the nodes at the base of the whorl of lateral shoots.
386b. The sexual organs are situated at the nodes of the whorled lateral shoots, and consist of antheridia and carpogonia. Most of the plants are monœcious, and both antheridia and carpogonia are often attached to the same node, the antheridium projecting downward while the carpogonium is more or less ascending. The sexual organs are visible to the unaided eye. The antheridium is a globose red body of an exceedingly complicated structure. The sperms are borne in several very long coiled slender threads which are divided transversely into numerous cells. The carpogonium is oval or elliptical in outline, the wall of which is composed of several closely coiled spiral threads enclosing the large egg.