A HISTORY OF BERKSHIRE THE LIVERWORTS (Hepatic^) The recorded species include : Scapania nemorosa Madotheca platyphylla Jungermannia albicans Metzgeria furcata - crenulata var. seruginosa - sphaerocarpa Pellia epiphylla ventricosa Aneura pinguis pumila Marchantia polymorpha bicuspidata Plagiochila asplenioides Lophocolea bidentata Frullania dilatata Radula complanata but the damp woods of Aldermaston Soak, Padworth, Hermitage and Finchhampstead are at present unexplored. CHARACE^ This curious group of aquatic plants, of which twenty-eight have been recorded as British, and eleven of which have been found in Berkshire, inhabit pools, streams and ponds, but are often of very ephemeral duration, occurring sometimes in immense quantities for one season and then disappearing for many years. They often occur in newly cleared out ditches and pools, and it may be that the competitive growth of leafy forms of phanerogams such as Callitriche exert a malign influence by shutting out the sunlight, and that it is to this cause rather than to the exhaustion of the food supply that their short-lived duration is due. One of the rarest species, Nitella mucronata, was discovered in Britain for the fourth time by me in 1892, and then it filled up a large ditch for about 100 yards just on the border of our county at Godstow, and subse- quently I found it on the Berkshire side of the Thames. It existed in quantity till the following February, since which time I have been unable to find it in the ditch where it was so abundant. On the basic strata of the north of the county the species Chara vu/garis, C. contraria and C.fragilis, the latter chiefly as the var. Hedivigii, occur, the latter often in great quantity in the Thames tributaries. Tolypella glomerata is very sporadic in its occurrence, and for one year I noticed T. prolifera opposite the college barges at Oxford. On the more silicious Bagshot sands Nitella Jiexilis and N. opaca, the latter com- mon in Virginia Water, and the very handsome N. translucent are found, Pools of stagnant water, as at Wytham, Buckland and Cothill, yield the large species Chara hispida. FRESHWATER ALG^E Very little systematic work has been done at this group, but the county affords very rich hunting grounds not only in the marshes and ditches of the north but in the bogs and peaty moors of the south. In the saline meadow at Marcham Vaucheria dichotoma var. submarina occurs. 66
