ANNALS OF NATURAL HISTORY. 



XLI. — Oil the Structure of the Seta q/Tunaria hygrometrica. 

 By Edwin Lankester, M.D. 



The hygrometrical properties of the Funaria hygrometrica 

 have been long known to botanists, but as the movements 

 produced in it by its sensibility to moisture are very singular, 

 and as I am not aware of the subject having been dwelt upon 

 by any botanist, I have been induced to prepare the following 

 notice. This moss is one of the most common of the tribe, 

 being found abundantly on dry banks and on the soil that 

 barely covers the roots of full-grown trees ; but it especially 

 delights where the ashes of burnt wood cover the soil, and 

 thus it may be frequently seen restoring the colour of the 

 ground on those little black spots which indicate where the 

 gipsy has pitched his tent, or in the woods or by the side of 

 the hedges where wood has been burnt. The young thecae 

 make their appearance early in the spring, and in the months 

 of April or May may be found accompanied by a number of 

 dried setae as well as others in all stages of their growth. 

 If one of the dried setae be taken in the hand, and its lower 

 portion moistened with the ringer, the capsule will be seen 

 to turn from right to left, making two, three, or even more 

 complete revolutions ; if now the upper portion be moist- 

 ened in like manner, the capsule will turn round more ra- 

 pidly in a contrary direction. This phaenomenon is exhi- 

 bited whichever portion of the seta is first wetted. If both 

 ends are moistened at the same time, a tremulous wavering is 

 observed without any motion, but in a few seconds the cap- 

 sule begins to move in one direction or the other. The di- 

 rection in this instance is in some measure determined by the 

 quantity of moisture applied, but the upper part seems most 

 easily affected, and the motion arising from moistening it is 

 much more rapid than from the lower portion. If the cap- 

 Ann. Nat. Hist. Vol. 4. No. 26. Feb. 1840. 2 d 



