583 



unable to say, but I had to break the ice to procure the specimens sent. 

 The manner of using the leaves is to lay a number of them on the 

 burn, and as they dry to replace them by fresh ones. A friend of 

 mine, a native of Morganwg,* informs me that in that part the leaves 

 are mixed up with lard, so as to form an ointment ; he thought that 

 the leaves known by the above Cambro -British name were very much 

 larger than the size stated ; perhaps some other species may be used 

 by the Glamorganshire people for the same purpose, as the name only 

 indicates the "leaf for a burn by fire." — James Bladon; Pont-y-Pool, 

 March 8, 1843. 



[The plant sent by our correspondent as the *' Daill llosg y Tan'' of Gwent, we be- 

 lieve to be the common pondweed, — Potamogeton natans. — Ed^ 



288. On the injiueiice of Light in 'producing the Green Colour of 

 Plants. About Christmas, 1841, I was searching in a wood, chiefly 

 oak, for some lichens to decorate the perches in a glazed case, in- 

 tended for the reception of some ornithological specimens. I hap- 

 pened to turn over with my foot a piece of oak bark, about fifteen 

 inches long : the side next the ground (the external part of the bark 

 when in situ) was covered with lichens of the most vivid green, quite 

 as bright as that of any leaves in early summer, not the pale colour of 

 young shooting leaves, but of those arrived at mature growth. From 

 the appearance of the grass under and on each side of the place where 

 the bark had been, it had evidently lain there at least all the previous 

 summer : yet I have never seen any lichens of the same or any other 

 species, exposed to the full light of " day's garish eye," in the least 

 approaching the vividness of the colour in the specimens alluded to 

 above. — Id. 



[The following passage relating to the Algse, which are nearly allied to the Lichens, 

 occurs in the Introduction to Harvey's 'Manual of British Algae.' After mentioning 

 the three principal varieties of colour among the Alga;, namely, grass-green, olivace- 

 ous-brown or olive-green, and red, the author states that the first of these colours is 

 characteristic chiefly of such species as are " found in fresh water, or in very shallow 

 parts of the sea, along the shores, and generally above half-tide level,'' the great mass 

 of the green Algae being inconsiderably submerged. " The olivaceous-brown or olive- 

 green is almost entirely confined to marine species; * * the red also is almost exclu- 

 sively marine, and reaches its maximum in deep water. * * How far below low- 

 water mark the red species extend has not been ascertained, but those from the extreme 

 depths of the sea are of the olive series in its darkest form. For the colours of these 

 last it has puzzled botanists not a little to account. It is well known that light is ab- 



* Morganwg, the eastern part of Glamorganshire. The above names are sometimes 

 applied in a more extended manner, indicating the whole of each county. 



