12 INTRODUCTION. 



such bulbils freely on the under surface of some of its fronds, 

 so that the introduction of a single plant in a greenhouse is 

 soon followed by an abundance of young plants on the floor 

 and shelves and in the pots of other plants. Several exotic 

 species of Asplenium develop these bodies on their fronds, and 

 may be seen in cultivation with the upper surface of the fronds 

 crowded with young plants, each bearing four or five fronds 

 and furnished with roots. 



Several species of our native ferns in cultivation have pro- 

 vided examples of the phenomenon known as Apogamy in which 

 the prothallium instead of producing Antherids and Archegones 

 has developed buds which have grown into perfect fern-plants. 

 In the following native species yet another abnormal process 

 Apospory has been observed: Lady Fern, Angular Shield- 

 fern, Male Fern, Hart's-tongue, Common Polypody, Mountain 

 Bladder-fern, and Bracken ; this consists in the development of 

 prothallia from fine outgrowths at the tips of the fronds. As 

 these cases are exceptional and have occurred chiefly under 

 cultivation, there is no need to deal with them at length in this 

 work. 



In studying technical works on ferns the general reader 

 finds a difficulty in readily remembering the significance of the 

 terms which denote the degree of frond division. We must, to 

 a large extent, use the same terms, for they have no equivalents 

 in single English words ; but the matter may be much simplified 

 by means of a few illustrations. Starting with such an unfern- 

 like frond as that of the Hart's-tongue, we have the frond in its 

 simplest form. It is strap-shaped, with a heart-shaped base. 

 We may take the opportunity to note that whilst the stalk is 

 known as a stipes, its continuation through the frond proper 

 the leafy expansion is styled the rachis. Here the rachis, like 



