CLASSIFICATION OP VEGETABLE PEEPAEATIONS. 407 



Ferns. — The parts of this curious tribe of plants most in- 

 teresting for microscopic examination, are the reproductive 

 organs or sporangia which are situated on the under surface of 

 the fronds, and consist of yellowish brown masses of capsules, 

 in which the seeds or spores are contained. Ferns should be 

 gathered before the capsules are quite ripe, otherwise, in 

 drying, these delicate structures are apt to burst, and the 

 contained spores are scattered to some distance by the action 

 of an elastic spiral spring, which forms a band or zone on the 

 upper part of each capsule. After having been carefuUy 

 dried, small portions of the frond containing the sporules 

 should be fastened by some cement to any of the large discs 

 before described at page 319, or the very flat kinds may be 

 mounted between glasses with Canada balsam. The capsules 

 are best examined as opaque objects, with a power varying 

 from forty to one hundred diameters, when illuminated by a 

 Lieberkuhn, or by the side reflector. As almost every kind of 

 fern, whether British or foreign, is more or less beautiful, it 

 would be needless to particularize any individual specimens ; 

 those, however, presently to be enumerated under the head 

 of spores, wiU serve to show both the capsules and their 

 contents. 



Spores. — These, which are analogous to seeds in other 

 plants, should be examined either as opaque or as transparent 

 objects, with a magnifying power from two to three hundred 

 diameters ; the list might well include the whole of the fern 

 tribe, as all are more or less beautiful, but the following may 

 serve as a guide to some of the most interesting specimens : — 

 Adiantum nigrum, Lomaria spicant, 



capillus veneris, Lycopodium, 



Aspidium aculeatum, Pteris elegans, 



Davallia Canariensis, hastata, 



Grammitis ceterach, Polypodium vulgare, 

 Hymenophyllum Tunbridgense, Scolopendrium vulgare, 

 Wilsoni, Todea Africana. 



