Fig. 17.—A, plant of Coleochæte, × 50. B, a few cells from the margin, with one of the hairs.
Much like Œdogonium, but differing in being branched, is the genus Bulbochæte, characterized also by hairs swollen at the base, and prolonged into a delicate filament ([Fig. 16], G).
The highest members of the Confervaceæ are those of the genus Coleochæte ([Fig. 17]), of which there are several species found in the United States. These show some striking resemblances to the red seaweeds, and possibly form a transition from the green algæ to the red. The commonest species form bright-green discs, adhering firmly to the stems and floating leaves of water lilies and other aquatics. In aquaria they sometimes attach themselves in large numbers to the glass sides of the vessel.
Growing from the upper surface are numerous hairs, consisting of a short, sheath-like base, including a very long and delicate filament ([Fig. 17], B). In their methods of reproduction they resemble Œdogonium, but the reproductive organs are more specialized.
CHAPTER V.
Green Algæ—Continued.
Order III.—Pond Scums (Conjugatæ).
The Conjugatæ, while in some respects approaching the Confervaceæ in structure, yet differ from them to such an extent in some respects that their close relationship is doubtful. They are very common and familiar plants, some of them forming great floating masses upon the surface of every stagnant pond and ditch, being commonly known as “pond scum.” The commonest of these pond scums belong to the genus Spirogyra, and one of these will illustrate the characteristics of the order. When in active growth these masses are of a vivid green, and owing to the presence of a gelatinous coating feel slimy, slipping through the hands when one attempts to lift them from the water. Spread out in water, the masses are seen to be composed of slender threads, often many centimetres in length, and showing no sign of branching.