OF MICROSCOPIC OBJECTS. E5 
the leaves are the reservoirs for the spores, which in many 
instances somewhat resemble green velvet, and are arranged 
in stripes, round masses, and other forms. The spores are 
usually covered with a thin skin, which is curiously marked 
in some specimens, often very like pollen-grains. The man- 
ner in which these spores with all their accompaniments 
are arranged, their changes and developments, afford almost 
endless subjects for study; different ferns presenting us with 
many variations in this respect totally invisible without the 
aid of the 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 ar- 
rangement of the spores, &c., is altered. The spores may 
be mounted as separate objects in the same manner 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 ezamina- 
tion 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 interesting 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 
