187 



animal and vegetable life, from meteorological causes, which has probably ever 

 been going on upon the earth's surface, deserves thoughtful attention, and if 

 it extended no further than the drying up of numerous ponds in a country sub- 

 jected to a continued amount of increased temperature, is a remarkable fact 

 in Natural History. 



[A number of drawings of minute microscopic Algals were displayed by 

 Mr. Lees, and were attentively examined.] 



Still, amidst destructive influences, novel conditions induce special growths 

 and appearances, and thus minute plants present themselves to view not ob- 

 servable at other times, and chiefly, if not entirely, under these altered circum^ 

 stances. 



I shall adduce two minute organisms that have come under my notice 

 this summer, and which only appear under conditions of high temperature, 

 that they take advantage of, and which therefore entitles them to the appella- 

 tion of Meteoric Plants. 



One of these is a little green, bubble-like Alga, that bears the name of 

 Botrydium granulatum, the generic term being derived from the Greek botrys, 

 the plant putting on the appearance of little bunches of grapes, more, in fact, 

 like an assemblage of minute bubbles of green glass. It is only on the ex- 

 posed mud of ponds that have lost their water that the Botrydium appears, 

 so that it is useless to look for it except in very hot summers ; and consequently 

 though abundant in particular places suitable for it in this very exception- 

 able season, years may elapse ere it appears again, and the beds of ponds 

 bereft of their water be exposed to view. By some authors this little Algal 

 is called Hydrogastrum, and is placed, as a genus of SipTwnem, among the Con- 



fervoid Alg<e. 



I have found this obscure Algal, under the circumstances adverted to, 

 during the present summer, not far from Dovedale, in Derbyshire; and in some 

 abundance in a secluded dried up pool at Mathon, in Worcestershire ; rather 

 plentifully at Powick Ham, near Worcester ; as well as at Colwall, in Hereford- 

 shire. It forms a green stratum of little globules in the first instance, which are 

 rooted in the damp soil, and chequered with white specks on the exterior sur- 

 face so that, on the mud of a dry pond where it is plentiful, the surface has the 

 appearance as if a hoar-frost had covered the ground, while the globules crackle 

 under the feet as when treading upon grass encrusted with frozen particles. 

 I have made magnified sketches of the plant ; but it is curious that the inflated 

 vesicles-similar to minute globules-are only the plant in its first stage of 

 growth, and not its ultimate appearance. The vesicles collapse without burst- 

 ing, and then present a concave appearance, like a mass of crowded Pezizce. 

 The vesicles previously separate now combine, and a green united crust or frond 

 presents itself to view, very much like an Ulva, to which tribe the Botrydium 

 bears considerable affinity, and indeed it was called an Ulva. by Linnaus. 



Though Dr. Greville has described and figured the Botrydium in his 



