yo THE MICROSCOPE. 



May, September, and October ; but some species are found in perfec- 

 tion 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 inte- 

 resting species of desmidiese and other fresh-water algae may be pro- 

 cured. 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 

 rotundifolia (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 up 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 gelatinous nature. It consists of a hyaline 

 substance, with a comparatively small quantity of a bright green en- 

 dochrome, disposed in little branches, and this is the Draparnaldia 

 glomerata. 



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 recognised as 

 Zygnema nitidum. In various parts there are other species of zyg- 

 nema, tyndaridea, mougeotia, mesocarpus, and many others. 



Keeping up the stream, and occasionally diverging a little on 

 either side of it, amongst the miniature bays and pools formed by the 

 sphagnum, on looking straight down into the water we shall probably 

 see at the bottom a little mass of jelly of a bright green, studded with 

 numerous brilliant bubbles of oxygen-gas. This is the general appear- 

 ance of most of the desmidiece, as Micrasteias, Euastrum, Closterium, 

 Cosmarium, &c. The spoon is also a handy tool in this case, though, by 

 practice, the finger will do nearly as well ; the chief difficulty arises 

 when the specimen is brought to the surface of the water, it not being 

 easy to get it out without losing a considerable portion of it. 



Little pools in the bog, made by the footsteps of cattle, are par- 



