The remarkable Hydrodictyon utriculatum, popularly known as “Water Net,” appeared some years ago in Blackroot Pool, Sutton Park, in enormous quantities, but shortly disappeared and has not been seen there since. It has also been recorded by Mr. T. Bolton as found in Bourne Pool, near Aldridge.
The large tribe of Volvocineæ is represented by the well-known forms of Gonium, Pandorina, and Eudorina, and by the typical Volvox globator, which, as is its wont, occasionally appears in some of the pools of the district in great profusion, only to vanish as capriciously. Mr. Bolton has recorded the rare and interesting Volvox globator ♂,—the Sphærosira volvox of Ehrenberg—as occurring in the small pool in the gravel pit near Blackroot Pool, Sutton Park.
Passing to the Zygnemaceæ, Vaucheriaceæ and other filamentous Algæ, we find a large number of species of Zygnema, Spirogyra, Zygogonium, Mesocarpus, Staurocarpus, Vaucheria, &c., occupying ditches, small pools and other stagnant waters; it is scarcely possible to take a bottleful of water from these stations in summer and autumn without finding examples of the curious modes of reproduction characteristic of these genera.
In running streams and in the still ponds of the district the long fronds of Enteromorpha, the dense tresses of brilliant green Cladophoræ and the graceful tufts of Stigeoclonium and Chætophora abound. The exquisite Cœtophora endiviæfolia reappears at intervals in Keeper’s Pool, Sutton Park; this species has also been found by Mr. Bolton in an old gravel pit at Hill Hook and in Earlswood reservoir.
The elegant Bulbochœte setigera is met with in small fragments in stagnant pools, and the singular Coleochœte scutata is to be found adherent to submerged water weeds.
The tepid waters of the South Staffordshire coal district are specially favourable to the growth of Oscillatorieæ, which form on their margins immense sheets of the deepest green velvet.
Several species of Batrachospermum (among which B. atrum is locally the rarest, having been found at Halesowen only) occur in small masses in clear streams, but they must be regarded as somewhat scarce plants. Lemania fluviatilis should be mentioned as common in the Avon and Severn, and the very rare Bangia atropurpurea as occurring on a water wheel in the former river at Stratford-on-Avon, although these habitats are somewhat beyond the limits contemplated in this sketch.
The Diatomaceæ of the neighbourhood do not appear to have been the objects of systematic study, and the only species of special interest which we remember to have found is the wonderful Bacillaria paradoxa, well known as a remarkable microscopic object from the strange manner in which its linear frustules glide over one another, so that the whole plant is incessantly assuming a different form. It has been found by Mr. Bolton, along with many other species, in a disused arm of the canal near Albion Station, and by the writer in a small stream near the same spot. A careful search would doubtless result in the discovery of a large number of representative species of this class.
In conclusion, we turn for a moment to the very beautiful tribe of Desmidieæ, and, although the district by no means abounds in the peaty bogs which are their especial haunts, a goodly list of ordinary species has been recorded. Sutton Park is the best locality for these plants, and in addition to the commoner forms of Micrasterias, Euastrum, Closterium, &c., which are here found in abundance, this habitat has yielded many rare and several new species, among which the following are worthy of special notice, viz.:—Micrasterias papillifera, M. Cruxmelitensis, M. angulosa, M. denticulata, var. lichmoides, and M. Americana, forma major; Cosmarium coronatum, Closterium directum, Cl. angustatum, and Cl. Pritchardianum; Penium closteriodes, P. Jenneri, and P. Nägeli.
A more detailed list of species is inadmissible, but the foregoing brief sketch will suffice to show that the Freshwater Algæ of the neighbourhood are tolerably abundant, and by no means devoid of interest.