DR YOPTERIS CRTS TA TA x MARGIN A LIS. 5 



that in the latter are seldom seen until a much later period. The 

 fronds of these offsets also sometimes develop their lower pair of 

 pinnae much at the expense of the rest of the frond. This is not due 

 to any injury, so far as I can see. In the fronds of young plants 

 growing directly from spores, the pinnae (figs. 3, 8) are usually short, 

 blunt, as in cristata, but they are perhaps narrower; they have a more 

 contracted, concentrated look than the pinnae of cristata. 



As the plants grow older the pinnae at the very apices of the 

 fronds retain their blunt character. The other pinnae of the upper 

 two-thirds of the fronds (figs. 2, 5, 6, 7, 10) grow, unlike those of cris- 

 tata^ long and acuminately pointed (except when one occasionally 

 finds a short, blunt pinna wedged between the long ones), and some- 

 times, not often, the pinnae of the lower third also. Usually these 

 lower pinnae remain short and are either blunt (fig. i) or slightly 

 pointed (fig. 9). The transition from the short, lower, to the long, 

 upper pinnae is sometimes gradual, sometimes abrupt. When abrupt, 

 the lower pinnae look very much like the pinnae of cristata^ and the 

 upper recall those of marginalis. In very large fronds — except at the 

 apices where the pinnae retain their bluntness in a somewhat modified 

 form — the long and short pinnae are alike acuminately pointed (figs. 4, 

 5, 6, 7). I examined perhaps two hundred plants of Dryopteris cris- 

 tata marginalis last summer, and feel satisfied that the older the plant, 

 the greater is the tendency of this fern to lengthen and point its pinnae 

 and pinnules. 



The pinnules never become much pointed. In the younger 

 fronds they are short, and rounded or blunt, their margins entire or 

 finely toothed, either all around or at the ends only. Later the 

 pinnules grow longer and narrower and the teeth become lobes, in 

 their turn toothed. The pinnules, especially in very large fronds, are 

 frequently irregular (fig. 7), pinnules little more than curves alter- 

 nating with others several times their length, giving the whole frond a 

 curiously distorted appearance. Sometimes entire clumps are affected. 

 Comparing a pinna of a young frond (fig. 8) with a pinnule taken from 

 a good sized plant (fig. pcz), the two are seen to be almost identical, 

 even in the veining. Again, when the plants grow older and the 

 pinnules grow longer and become lobed, each small lobe is very like 

 a pinna of the first fronds starting from the prothallus. The fern 

 thus, in a way, repeats the primary segments of the earlier fronds in 

 the secondary and ultimate segments of the later. One, of course, 

 finds plants in all stages of development, and taking also into con- 

 sideration the tendency innate in most ferns, to vary with different 

 environments, the variety of specimens of cristataxinarginalis is not 

 easily described. 



