OF MICROSCOPIC OBJECTS. 53 



sium, which is curiously marked in some specimens, often very 

 like pollen-grains. The manner in which these spores with all 

 their accompaniments are arranged, their changes and develop- 

 ments afford almost endless subjects for study ; different ferns pre- 

 senting us with many variations in this respect totally invisible 

 without the aid of a microscope. The hymenophyllums (of which 

 two only belong to England) are particularly interesting, and the 

 structure of the leaves when dried makes them beautiful objects, 

 often requiring no balsam to aid their transparency. Portions of 

 the fronds of ferns should be mounted as opaque objects, after 

 having been dried between blotting paper, when they are not 

 injured by pressure; but care must be taken to .gather them at 

 the right time, as they do not show their beauty before they are 

 ripe, and if over-ripe the arrangement of the spores, &c., is altered. 

 The spores may be mounted as separate objects in the same man- 

 ner as pollen, before-mentioned, and are exquisitely beautiful 

 when viewed with a tolerably high power. The number of foreign 

 ferns now cultivated in this country has greatly widened the field 

 for research in this direction ; and it may also be mentioned that 

 the under-sides of many are found to be covered with " scales" of 

 very beautiful forms. A small piece of the frond of one of these 

 may be mounted in its natural state, but the removal of the 

 " scales" for examination by polarized light will be described in 

 another place. The mosses also are quite a little world, requiring 

 but a low power to show their beauties. The leaves are of various 

 forms, some of which resemble beautiful net-work ; the " urns" or 

 reservoirs for the spores, however, are perhaps the most interest- 

 ing parts of these objects, as also of the "liverworts" which are 

 closely allied to the mosses. These " urns" are generally covered 

 by lids, which fall off when the fruit is ripe. At this period they 

 are well fitted for the microscope. The common screw-moss may 

 be found in great abundance, and shows this denudation of the 

 spores very perfectly. Many of these may be easily dried without 

 much injury, but they should also be examined in their natural 

 state. 



The student should not omit from his cabinet a leaf of the net- 

 tle and the allied foreign species, the mystery of which the micro- 

 scope will make plain. The hairs or stings may also be removed, 



