.288 FREAKS OF PLANT LIFE. 



in some palms, with a loud report, as sometimes 

 recorded, will be due to a like cause. The dryness 

 of the atmosphere inducing contraction in one series 

 of cells, greater than in another, produces a violent 

 rupture, as in the separation of the carpels of the 

 *' sand-box," accompanied by a sharp sound. 



Microscopists hold in great favour an object which 

 finds a place in almost every " cabinet," and consists 

 of the peristome of the common hygrometric moss 

 {Funaria hygronietrica). In this, and many other 

 species, especially /fj^7/z«//, the urn-shaped receptacles 

 which contain the spores are at first covered with a 

 lid, or hood, and when the latter falls away are seen 

 to be fringed with a single or double row of teeth, 

 called the peristome. These teeth converging in- 

 wards cover the spores, and prev^cnt their escape, 

 when expanded or recurved they permit of the free 

 discharge of the contents of the urn. This fringe 

 is exceedingly sensitive to moisture, opening and 

 closing when breathed upon, or as the moisture of 

 the breath evaporates. It is a very pretty and avail- 

 able illustration of a vegetable hygrometer. Some 

 bryologists object to this as a legitimate inference. 

 They assert that the movement is not vital, but is 

 merely mechanical, resulting from the diverse cha- 

 racter of the outer and inner layer of cells, of which 

 the peristome is composed. Admitting the structure 

 to be thus accurately described, it becomes a 



