Chapter III.
The Algæ.
BY A. W. WILLS.
The great class of Algæ includes the sea-weeds, together with a large number of plants, mostly of microscopic size and of simple cellular structure, which abound wherever fresh water is found, whether in the form of running streams or stagnant pools, or even as covering damp surfaces of ground.
A broad subdivision of the Algæ into three groups has been generally accepted by botanists, these being the Rhodosporeæ (red-spored), Melanosporeæ (dark-spored), and Chlorosporeæ (green-spored). The marine genera are distributed over all three of these groups; the freshwater ones belong almost exclusively to the last. The classification of the freshwater Chlorosperms is by no means satisfactory, but it is impossible to discuss it within the limits of this article.
It is to be regretted that scarcely any of the botanists of Birmingham have made the Algæ their special study; hence the information at our disposal is insufficient to enable us to group the recorded species with reference to their occurrence in the several adjacent counties. This is, however, the less important because the distribution of this class of plants is not dependent, to the same extent as that of Phænogams, either on climate or soil, though it is probably not altogether independent of either. Their abundance, therefore, is in pretty direct proportion to that of such spaces of water as afford favourable conditions for their growth.
Hence, as the neighbourhood of Birmingham is mostly characterised by light and porous soils, the habitats in which Algæ are to be found are somewhat restricted. There are, however, two conspicuous exceptions. The tract of land about seven miles from Birmingham, known as Sutton Park, embraces a singular variety of scenery and presents conditions highly favourable to algoid growth in the shape of clear springs and streams, large sheets of water, and a considerable area of peaty bogs. Again, the mining district of South Staffordshire and Worcestershire, popularly known as the Black Country, affords among its pit-banks a great number of pools which are seldom dried up even in the hottest summer, and many of which are partially fed by water from adjacent mines or engines. Their number has been much diminished during the last few years by the operations of the South Staffordshire Mines Drainage Commission, but is still very large and these constitute a rich hunting ground to the student of freshwater Algæ.
The brief notes which follow must be regarded merely as an indication of the general character of this branch of the Midland Flora. Any attempt systematically to enumerate the recorded species would far exceed the necessary limits of this notice.
The great group of so-called Unicellular Algæ is universally distributed, and the familiar forms included under the ill-defined genera of Pleurococcus, Glœocystis, Tetraspora, Pediastrum, &c., are found abundantly in this district wherever conditions favourable to their growth are present. Among these low forms may be mentioned Apiocystis Brauniana, parasitic on larger Algæ in stagnant pools; the extremely rare Mischococcus confervicola, recorded as found near Stafford, and Polyedrium tetrahedricum found on decaying leaves in a small pit near Sutton. Ophiocytium cochleare, until lately regarded as a very scarce plant, is not uncommon in similar habitats.