BOTANY THE STONEWORTS {Characea) 1 The Charas or stoneworts constitute a well-defined group of aquatic plants, the English appellation being given to them on account of the quantity of lime that is secreted by some of the species. They are always submerged, and are to be found in ponds, pools, lakes and streams, affecting chiefly quiet waters, although sometimes occurring in rapidly running brooks. They are often the first kind of vegetation to occupy pools that have been newly formed, such as water holes in clay pits and reservoirs that are uncovered. In such situations they may sometimes be observed to have filled nearly the whole of the available space, to the temporary exclusion of other vegetation. It is also noteworthy that they occasionally die away rapidly from an apparently congenial habitat, and although they may have fruited abundantly, and the mud below con- tains multitudes of their fruits, they do not reappear for several years. Apparently they have exhausted the constituents in the water that are necessary to their existence, and do not start a fresh growth until the conditions are again favourable for that purpose. It may happen that, in the meantime, other aquatic plants, such as water-buttercups and pond- weeds, have occupied the site, and the Characeas can only find a pre- carious existence, or fail to reappear for an indefinite period. In the waterways of the Fen districts they often occur in enormous quantities, and as their tissues contain a large proportion of mineral matter, they add annually in their decay an appreciable amount of soil. Their presence may often be detected by the foetid odour they exhale when left uncovered by receding waters. The only two forms mentioned by Abbot (1798) are Chara vulgaris and C. totnentosa, the latter probably that now known as C. hispida. The most noteworthy record given below is that of Nitella mucronata, found in 1882 by C. H. Davis, after having been unrecorded in Great Britain for fifty years. Chara fragilis, Desv. Frequent Tolypella glomerata, Leonh. Rare ; Lea- var. Hedwigii. Leagrave, Sundon grave, near Bedford „ capillacea. Totternhoe — intricata, A. Br. Rare ; Brammingham, — contraria, Kuetz. „ Sundon — hispida, L. Not common Nitella mucronata, Kuetz. Rare ; River — vulgaris, L. Frequent Ouse, Bedford, River Ive/, Sandy var. longibracteata. Biscot — opaca, Ag. Frequent alg^: 2 Practically the only available information concerning the freshwater alga? is in Abbot's records. A few microscopists have examined speci- mens from time to time but have kept no records, and apparently have had no means of determining species. Mr. E. M. Holmes, curator of the Museums of the Pharmaceutical Society of Great Britain, has been 1 By James Ssunders, Luton. 2 Revised by E. M. Holmes, curator of the Museums of the Pharmaceutical Society of Great Britain.
