50 FOOTNOTES FROM 



marvellous reflection as that of the urn-mosses. It is 

 generally supported on a very delicate silvery stem ; and 

 is at first round, gradually splitting as it becomes ripe 

 into two or four valves, which bear a close resemblance 

 to the calyx or corolla of flowering plants. In the cen- 

 tre of this calyx-like organ may be seen a tuft of delicate 

 straw-coloured hairs, like floss silk, with the spores or 

 seeds in the form of minute yellow dust intermingled. 

 These hairs or filaments are spiral, highly elastic, and 

 hygrometrical, twisting and writhing even upon the field 

 of the microscope ; and like the spring-like ring round 

 the fruit-vessel of the fern, serve by their coiling and 

 uncoiling, in certain states of the surrounding atmosphere, 

 to scatter abroad, even to a considerable distance, the 

 powdery seeds imbedded among them. This is a very 

 curious and wonderful piece of mechanism, and highly 

 deserving of microscopical examination. 



One genus of this interesting family called Riccia, 

 floats on the surface of stagnant waters, and bears a 

 superficial resemblance to the common duckweed. The 

 fronds are destitute of radicles when growing on the 

 surface of ponds and ditches ; but if the water be removed 

 by evaporation or draining, or the plant thrown on the 

 soil at the margin, they become smaller and fasten them- 

 selves firmly to the ground by numerous fibrous rootlets ; 

 a beautiful example of the ease with which these humble 

 plants accommodate themselves to altered circumstances. 

 They have many air-passages between the cells, which 

 enable them to float on the water. The under surface 

 is covered, to a greater or less extent, Avith thin scales, 

 which form most beautiful microscopic objects when 



