COLLECTING OBJECTS. 251 



spirits quite spoils the appearance of the frustules, as it 

 dissolves the endochrome. 



" There is another salt-marsh a little farther down the 

 same railway, at Higham, which it would he well to 

 explore. The most favourable months for procuring dia- 

 tomacece, are April, May, September, and October; but 

 some species are found in perfection as early as February, 

 and many as late as November, and a few at all times of 

 the year. There is a piece of boggy ground near Keston, 

 beyond Bromley, in Kent, where the river Ravensbourne 

 takes its rise, where many interesting species of desmi- 

 dacece and other fresh- water alga? may be procured. From 

 Bromley, walk on towards Keston, passing near Hayes 

 Common and Bromley Common on the right. Continue 

 for about another half-mile along the road, and then turn 

 to the right hand ; pass the reservoirs, and approach an 

 open space where there is a bog of about a quarter of a 

 mile in extent; and tending towards the right, make your 

 way amongst heaths, ferns, mosses, and the beautiful 

 Drosera rotivndifolia (sun-dew), to the lower part of the 

 little stream rippling through a sort of narrow trench in 

 the Sphagnum, &c. By working your way tip the stream, 

 you avoid the inconvenience which would otherwise be 

 experienced of the water being rendered turbid, in con- 

 sequence of having to tread in the boggy ground. In the 

 centre of the little stream may be observed something of a 

 pale pea-green colour flickering about in the current, 

 which, on your attempting to grasp, most likely eludes 

 you, and slips through the fingers, from being of a gelatin- 

 ous nature. It consists of a hyaline substance, with a 

 comparatively small quantity of a bright green endo- 

 chrome, disposed in little branches, and this is the Dra- 

 parnaldla glomeraia. Another object is a mass of green 

 filaments, rather harsh to the touch, and very slippery. 

 When viewed with a lens of moderate power, each filament 

 is seen to be surrounded with several bands of green dots, 

 looking like a ribbon twisted spirally, and may be recog- 

 nised as a species of Zygnema. In various parts there 

 are other Zygnemacece, as spirogyra, mougeotia, mesocarpus, 

 and many more. 



" Keeping up the stream, and occasionally diverging a 



