CH. XXXII] LOPHOSORIA 283 



hairs and no scales : one of them {G. pectinatd) has advanced beyond the rest 

 in several distinct features: for instance it has attained structurally to 

 solenostely : further its sorus bears more numerous sporangia than the rest 

 of the family, but the spore-count from each is relatively low. The sporangia 

 having only short stalks and median dehiscence are of a type that requires 

 "elbow-room" for the shedding of the spores, which the crowding of the 

 sorus mechanically prevents. In fact the sorus of G. pectinata suffers from 

 a condition of dead-lock. An escape from this difficulty would, however, 

 be possible by one or more modifications such as these: (i) by replacing 

 median by lateral dehiscence, (ii) by increasing the length of the sporangial 

 stalk, (iii) by extending the area of the sorus, (iv) by elongating the 

 receptacle. None of these have been adopted by the Gleicheniaceae, and 

 G. pectinata shows in consequence a soral state advanced to the point of 

 inefficiency. But the Cyatheaceae all have a lateral dehiscence: in this and 

 in other ways they have resolved the difficulty of a dead-lock. We may be 

 prepared to find among them, as still relatively primitive Superficiales, some 

 outlying species which share certain characteristics of the more advanced 

 Gleicheniaceae, but have escaped from their disabilities. Such links exist in 

 Lophosoria and Metaxya, which have been variously treated by systematists; 

 they are related directly with AlsopJiila, a genus which in soral character 

 may be held as the most primitive of the Cyatheaceae. Such outlying Ferns 

 thus appear as synthetic types, connecting the Gleicheniaceae with the 

 Cyatheaceae. On these grounds they call for careful examination. 



Lophosoria qiiadriphmata Gmel. 



The Fern so named has always been regarded as an outstanding species: 

 but, as its synonymy shows, it has been variously classified ("Studies in 

 Phylogeny, II," Ann. of Bot. xxvi, p. 279). Though it was constituted the 

 type of a substantive genus by Presl (1848), it was placed by Sir \V. Hooker 

 in AlsopJiila {Species Filicwn, i, p. 47), as A. pruinata Kaulf. Its characters 

 are, however, so distinctive that it will be best to uphold Presl's genus 

 Lophosoria, of which it is the sole species. The best description of this Fern 

 is given by Jenman in his Synoptical list of Jamaican Ferns. It is widely 

 spread in the Western Tropics as a low-growing Tree-Fern of forest shade, 

 with short upright stem, only about 3 feet high, and about 3-4 inches in 

 diameter, bearing spirally arranged leaves 6- 10 feet long, and repeatedly 

 pinnate, but with fine segments, and open venation. The large leaf is of the 

 Cyatheaceous type, which with the upright stem gives the plant the 

 appearance of a low-growing AlsopJiila. But the dense vestiture is of soft 

 hairs, no scales being present even on the leaf-bases. Associated with each 

 leaf-base is usually an abaxial bud, which may remain dormant in the upper 

 leaves, but at the base of the plant the buds develope into runners, which after 



