THE FERN BULLETIN 



35 



Poly stick urn ungulate, Nephr odium filix-mas, Poly- 

 podium vulgar e } and Scolopendrium vulgar e. In pro- 

 ducing the prothallia it has been found that the sporan- 

 gia begin to form but at a certain stage in their growth, 

 the spore-case becomes aborted and the prothallium 

 forms from its stalk. In other species, however, es- 

 pecially those with finely divided tips, the slender pro- 

 jections if pegged down on the soil will originate new 

 prothallia. One of the most interesting things con- 

 nected with this whole subject is the discovery of a 

 form that is characterized by both apogamy and apos- 

 pory. This form, in the complicated terminology of 

 British fern growers, is called Lastrea pseudo-mas 

 percristata apospora. It produces prothallia upon the 

 fronds and new plants upon these prothallia without 

 the need of eggs and sperms, in this way short circuit- 

 ing the usual course of fern growth. 



An Evergreen Cvstopteris. — It is well known 

 that the delicate little bladder fern ( Cystopteris fra- 

 gilis) is one of the first, if not the first of our ferns 

 to appear in spring. Long before the ordinary ferns 

 have begun to unfold, the bright green fronds of this 

 species may be found fully spread. The heat and dry- 

 ness of midsummer seem more to be feared by this 

 fern than the cold, and by August it is difficult to 

 find good specimens. Like the slender cliff brake, the 

 fronds are inclined to wither and disappear except in 

 the coolest of shadiest ravines. As the weather grows 

 cooler the fronds of Cvstopteris may again appear, but 

 die at the approach of winter. In the milder climate 

 of the British Isles, there is a variety of this fern that 

 remains green throughout the winter. It "s known as 

 Cystopteris fragilis sempervirens and has recently been 

 found in Scotland. 



