METHODS OF STUDY. 73 



gin. There being an indusium present, we are directed to C, 

 where we find four statements. Our fern agrees with the 

 second, as the indusium is formed of a reflexed portion of the 

 frond. Passing to D we find it agreeing with the first state- 

 ment. Passing to E, the statement, " Sporangia at the ends of 

 the veins, borne on a reflexed portion of the margin of the 

 frond," answers our purpose, and the marginal reference indi- 

 cates the genus Adiantum. Under this genus (p. 89) we find 

 two statements designated by *, and ** ; the latter referring to 

 the " dichotomously forked " fronds, answers our purpose, and 

 we find our fern to be number 5, Adiantum pedatum L., the 

 scientific name of the Maidenhair, which we can now place in 

 our description. Were we in Florida or any of the Southern 

 States, instead of A. pedatum we would probably have found 

 the Venus' Hair (A. capillus-veneris), or in California the Cali- 

 fornian Maidenhair (A. emarginatuni), either of which would 

 agree with the common Eastern species in all respects save the 

 method of branching of the frond and the shape of the pinnules. 

 In like manner we can trace any of our native species to their 

 scientific names, by carefully noting their structure and methods 

 of fruiting. 



1 53. In a few ferns it will be necessary to exercise great 

 care in the examination of the indusia. In the genera Cystop- 

 teris, Dz'cksom'a, and Woodsia, and in a few species of Dryopteris, 

 the indusia wither away after fruiting, so that one is likely to 

 classify them under the non-indusiate genera if he carelessly 

 examines them in this condition. In such cases a large number 

 of sori should be carefully examined, and the least trace of an in- 

 dusium should be noted. Five sixths of our genera, including 

 four-fifths of our species, are indusiate. 



1 54. Fern Allies. In determining the species of the fern 

 allies the method of procedure is quite similar to that indicated 

 above for the Maidenhair, in each case referring the plant to its 

 proper order. The specimens must be in fruit, and in the case 

 of Equisetum must include both sterile and fertile shoots. As 

 the species of Isoetes differ mainly in the size, character, and 

 markings of the spores, they will require a microscope with 

 micrometers for successful determination, though some can be 

 identified with a lens if the life habits are also known. 



