Page:VCH Suffolk 1.djvu/113

 BOTANY minute, and in order to obtain these some advice is necessary as they are not visible to the naked eye ; these forms are often found about the stems and leaves of constantly submerged plants, such as Utricu/aria, Myriophyllum, Nuphcr, Nymphaea^ Potamogeton, Sphagnum, &c. To collect from plants like these it is best to remove them (or parts of them) from the water with as little mud as possible and allow them to drain for about a minute, after which they should be gently squeezed over a wide-mouthed bottle. Gatherings made in this way are usually very rich in minute species. FRESHWATER ALGAE Only a moderate number of species have been noted as yet from the county ; this is due to lack of local workers during recent times, most of the records being old ones. Excluding diatoms, not more than forty genera and less than seventy species have been recorded. The districts about Tuddenham, Bradwell, Belton, Bury, Lound, and Ipswich, would certainly yield further results if worked. Among these recorded plants is the beautiful netted-purse plant, Hydrodictyon utriculatum, found at Bungay and other places. About ten genera of unicellular plants, excluding diatoms and desmids, are known to occur ; these include the pretty coenobial genera Scenedesmus and Pediastrum. Volvox globator is frequent, and V. aureus is probably present ; the latter can be distinguished from the former by its smooth spores and smaller size. The Conjugatae are represented by seven genera including the Desmidiaceae, only four genera belonging to the latter being recorded. The genus Vancherla is well represented, by six species, including V. dichotoma, which is seldom absent from maritime counties. The beautiful orange-coloured aerial algae, Trentepohlia {Chroolepus) aureum occurs on trees. The two British species of the delicately-branched genus Draparnald'ia are frequent. The gelatinous genus Chaetophora is represented by two species. As only two or three species of the Oedogoniaceae are known to occur, it is evident that more work can be done in this group. The remaining genera of the green algae which are known are those of common occurrence. The blue-green algae usually known as the Cyanophyceae (Myxophyceae is an earlier name) are represented by about fourteen species under eight genera, the genus Oscillatoria being represented by seven species. The only freshwater algae belonging to the Red Algae that are recorded are Batracho- spermum monUiforme and B, vagum, both very elegant species, and a species of Lemanea. DIATOMS This well-known group of plants includes both freshwater and marine species, as well as some that are usually only found in brackish water, or sometimes in the latter as well as in freshwater, or, in the case of some species, in either marine or brackish water. These are unicellular plants of very varied form ; they occur wherever water is constantly found ; they differ from all the other algae in having their cell-wall impregnated with silica, which prac- tically renders them — as regards their form and markings — indestructible, hence large fossil- deposits of them are found which are used commercially for various purposes, one important one being in the preparation of dynamite. The cell-walls are beautifully and symmetrically sculptured, although they are extremely thin. A fair number of species are known for the county, about 200 species under about fifty genera ; this includes the strictly maritime species. The genus Gyrosigma {Pkuroslgma), with its finely marked cell-walls, is well represented by twenty species. Under the genus Navicula (including Pinnularia) about forty species are recorded, and for the genus Nitzschia about twelve species. The genera Stauroneis, Gom- phoncma, and Synedra, are represented by from four to six species each, while the genera Surirella and Epithemia have eight and five species respectively, the genus Amphora also having five. None of the other genera are represented by more than four species, the genera Campylodiscus, Eupodiscm, Cocconeis, and Amph'iprora, have each several species. Fewer species are recorded for the genera Cymbella, Coscinodlscus, Actinocyclm, Cydotella, Tryhlionella, Cymato- pleura, Cocconema, Doryphora, Podosphaenioy Rhiphidophora, Aferidion, Bacillaria, Odontidium, Fragi/aria, Achnanthes, Achnanthidium, Rhahdonema, Diatoma, Grommatophora, Tahellaria^ Amphitetras, Biddulphia, Podoiira, Melosira, Orthoura, Maitoglota, Encyonema, Colletsnema, and Schizonema, the species recorded usually varying from one to three. 75