FERN-FLORA OF CANADA. 



227 



species of jilaiit. Tluis : Ciisfopffi.riA fiwiiUs is tlje name apj)lie(l to nil the iiidi- 

 vidual.s (themselves un(listiii<,'uisliahle from each other) of this particular species 

 of plant, — Ci/t^foph'viti bein^' the generic, /r«',7///.s' the s^jecifie, term. 



Varietik.s. — AH th(! individuals of a species are not exactly alike, however, 

 either in plants or animals We know that in the human sjiecics the j)eople of 

 dilierent parts of the earth are in some respects dillerent from M>ach other. 

 Although all dogs are of one s|)ecies, yet there nrc many kinds of dogs that are 

 easily recngnized fnjm each otlier, such as terriers, hniiiids, and spaniels, and these 

 ar(! classiti'd and named as varieties. It is exactly the same in the case of ferns 

 and other j)lants. The last specit^s mentioned, (Ji/i^frtpfcn's/ra'/ili)^, fringes the sea- 

 shores and islands and the rocky banks of our lakes and streams, and varies in 

 size, and in tlie form and division of its fronds, in diiFercnt situations ; but this 

 si)ecies also extends over a large portion of tin; globe, l)eing e<pia11y at home on 

 the Greenland and Labrador shores, in gulches on the highest snowy j)eaks of 

 Colorado, on winterless islands like Madeira, in Mexico, various piirts of .Si'uth 

 America, Australia, Africa and Asia. It is to be expected that this little wan- 

 derer will vary in appearance, dwarfing wh«'re it meets with lack of heat or 

 moisture, becoming almost an evergreen where it has no severe winter to contend 

 with, swelling out to large size and becoming of soft juicy texture where it grows 

 in a mild saturated atmosphere. In such ways, Varieties are produced, and when 

 these varieties ajipear to be sufficiently constant, and not the mere result of tem- 

 porary surroundings, nunes are given to distinguish them. The name of the 

 variety has to be added to the names of tlie genus and species, and thus it comes 

 that some of the ferns have three, instead of two, names. 



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How the different Genera of Ferns are known. 



The most [irecise distinctions between the difl'eront genera are found (1) in the 

 nature and branching of the minute veins in tlie divisions of the frond-, — whether 

 they form a connected net-work or are spread out, simp e or forked, like a fringe; 

 (2) in the position of the fruit dots (called Sori) on the frond, and whether tlie >iori 

 are separate from the veins or connected with them at llieir points, or sides ; (.3) 

 in the absence or presence of a spocid involucre or general covering for the sori or 

 masses of spore cases, formed by the incurving of the frond-maigin ; and (4) in the 



