40 



But certain characters of the sporophyte, notably the beauty of 

 the peristome and the ease with which it may be made to illustrate 

 the hygroscopic nature of moss peristomes in general, are what 

 especially commend Fimaria for use in botanical instruction. It 

 is, I believe, a sound principle in the pedagogics of natural his- 

 tory to select illustrative material now and then which is bound 

 to excite the interest and admiration of the most indifferent pupil. 

 It can be readily understood that in its abuse this motive might 

 lead to a selection which would interfere with a proper perspec- 

 tive of the subject as a whole, but, in the present case, the features 

 in which the peristome of Funaria differs from the type most com- 

 mon in the mosses are of little importance to the general student. 



For the best demonstration of the workings of the peristome, 

 the plants should be collected and dried when the capsules are 

 mature and brown and a little before the opercula are ready to 

 fall, which, in the neighborhood of New York, is mostly in June 

 and July. In this dried condition, they may be preserved indefi- 

 nitely. When the study of the matured sporophytes is begun, 

 some of them, still attached to the gametophytes, may be placed 

 in a glass of water and the student's attention directed to the un- 

 twisting of the seta as it absorbs the water. Then, on holding 

 one of them in the air a few moments, the seta is seen to twist 

 again. These movements of the seta under changing conditions 

 of moisture were, with little doubt, what suggested the specific 

 name hygrometrica to Linnaeus. Finally, the probable relation 

 of these movements to the dispersal of the spores may be sug- 

 gested to the student if he fails to think of it himself. The 

 amount of soaking required to remove the operculum depends 

 largely on the degree of maturity of the capsule at the time of 

 gathering. The act of throwing off the operculum and the re- 

 lation of the annulus to the process can best be observed if a few 

 capsules are placed in a large drop of water on a glass slide or in 

 a shallow watch-glass. After the removal of the operculum and 

 annulus, the capsule may be allowed to dry and if it can then be 

 balanced on its back with the mouth directed upward, the peris- 

 tome as a whole may be examined to advantage by reflected light 

 under the ordinary lower powers of the compound microscope. 



