i8 Our Native Ferns. 



i. Mode of Growth. — Ferns vary greatly in their method of 

 growth, yet each species has a plan which, within certain limits, is 

 fixed and definite. Some, like the common brake, have their 

 fi'onds rising from more or less distant portions of the creeping 

 rootstock. Others are tufted, many fronds rising irregularly in a 

 cluster, while still others grow in crowns or circles, the later 

 fronds continually rising within the older ones. In the grape-ferns 

 {Botfychium) the roptstocks usually produce a single frond each 

 season, the bud for the succeeding year growing within the base 

 of the common stalk. 



3. In many there is a tendency to dimorphism, the fertile or 

 fruit-bearing fronds differing to a greater or less extent from the 

 sterile ones. In a few species, like the sensitive-fern and the 

 ostrich- fern (0«oc&a), this is carried so far that the sterile and 

 fertile fronds bear no resemblance to each other, and in one in- 

 stance have been mistaken for different species and so described. 



4. Variation. — The same species will often present wide dif- 

 ferences in the size of the fronds. This depends to some extent on 

 the character of the soil and the ordinary climatic conditions. For 

 example, the lady-fern {Asplenium filix-fcemina), which in ordi- 

 nary locations grows from two to four feet high, in mountainous 

 regions is sometimes reduced to from three to six inches, when it 

 forms the var. exile. In like manner the marginal shield-fern ' 

 (Aspidium marginale) usually two or three feet high, is reduced to 

 five inches when growing on rocky cliffs, and yet regularly pro- 

 duces fruit.* 



5. In some cases there is a tendency to variation in size that 

 cannot be referred to soil or climatic influences. The common 

 grape-fern (Botrychium Virginianuin) will be found in some 

 localities to vary from six inches to two feet in height, all well 

 fruited and matured, and with the extreme sizes growing within a 

 pace of each other in the same soil and with the same environ- 

 ment. The other species of the same genus present similar vari- 

 ations, and judging from size and external appearance alone, a 

 regular gradation of forms might be arranged from the most di- 

 minutive undivided forms of B. simplex to the largest of B. Vir- 

 ginianuin. 



6. Another tendency to variation is noticed in the forking of 

 fronds either at the summit or at the ends of the branches. The 

 hart's-tongue {Scolopendrium) is frequently forked at the summit, 



* Compare Bulletin Torrey Botanical Club, October, 1878. 



