278 NEMATOGEN.E. 



Rivularia echinata. (English Botany.) 



Globose, very minute, dark coloured, compact. Threads 

 fastigiate, attenuated upwards to the apex, closely cohering, 

 articulated, heterocysts basal, globose. Sheaths very narrow, 

 almost inconspicuous. 



SIZE. Trichomes '007 mm. at base, -25 mm. long. 



Chcetopliora punctiformis, Kutz. Tab. Phyc. iii., p. 4, t. 18, f. 

 2. Rabh. Alg. Eur. iii., 386. 



Echinella articulata, Eng. Fl. v., p. 398. Eng. But, ii., t. 

 2555. Harv. Man. 187. 



Conferva echinata, Eng. Bot. i., t. 1378. 



Conferva echinulata, Gray. Arr. i., 310. 



In lakes, ponds, &c. 



This minute species, which was first described and figured in " English 

 Botany," appears to have been unknown on the Continent. We have 

 received it from several localities beside the original one of Ellesmere. 

 It is one of the Algae which are associated with the phenomenon called 

 " Breaking of the meres," thus alluded to by Professor Dickie in his 

 " Botanists' Guide' 1 (p. 310) : " For some years excursions were made 

 with the students of my botanical class to a loch on the estate of Parkhill, 

 about four miles north-west from Aberdeen. The sheet of water in 

 question is about a quarter of a mile in its greatest length ; on almost all 

 sides it is surrounded by extensive deposits of peat, with the soluble 

 matter of which a great proportion of the water passing into the loch is 

 impregnated. The locality was generally visited in the beginning of 

 July ; nothing particular had ever been observed till the summer of 1846, 

 when my attention was arrested by a peculiar appearance of the water, 

 especially near the edge, but extending also some distance into the loch. 

 Numerous minute bodies, with a spherical outline, and varying in size 

 from 1 24th to l-12th of an inch in diameter, were seen floating at different 

 depths, and giving the water a peculiar appearance. In some places 

 they were very densely congregated, especially in small creeks at the 

 edge of the loch. A quantity was collected by filtration through a piece 

 of cloth, and, on examination by the microscope, there could be no doubt 

 that the production w;;s of a vegetable nature, and a species of Rivularia; 

 one, however, unknown to me, and not agreeing with the description of 

 any species described in works to which I had access. Specimens were 

 sent to the Rev. M. J. Berkeley ; he informed me that the plant belonged 

 to the genus mentioned, and stated it to be Rivularia echinulata, Eng. 

 Bot. Along with it, but in very small quantity, I also found another 

 plant, Trichormusjlos-aquce, Bory. 



" In the first week of July, 1847, the same species were obsei-yed 

 similarly associated, but the Tfichormus was now more plentiful, with- 

 out, however, any apparent corresponding diminution in the quantity of 

 the Rimdaria. 



" In July, 1848, it was observed that the Riiularia was as rare as the 

 Trichormus had been in 1846 ; to the latter consequently the water of 

 the loch now owed its colour, which was a very dull green; the colour, 

 however, becomes brighter when the plant is dried. In neither of the 

 seasons mentioned was it in my power to make any observations on the 

 colour of the loch earlier or later than the date above mentioned, conse- 

 quently nothing can be added respecting the comparative development 



