XXXV] DISTRIBUTION 327 



of separating the Dicksoniaceae from the Cyatheaceae. Accordingly the 

 latter name is here used in a restricted sense, as excluding the marginal 

 Dicksoniaceae. 



Some of these ancient Families of Ferns are represented to-day only by 

 a single genus {Matonia, Dipteris), or even by a solitary species {Loxsoina, 

 T/iyrsopteris, LopJiosoria, Metaxya, Stromatoptcris, Platyzomd). This immedi- 

 ately suggests antiquity. It therefore becomes a que.stion of interest to see 

 what is the distribution of such Ferns to-day, and how it compares with that 

 of the past. The facts for several of the Families here treated have been 

 supplied in succinct map-form by Prof Seward, in his Hooker Lecture of 

 1922 {Journ. Linn. Soc. xlvi, p. 219). The Map A shows approximately the 

 present distribution of the Gleicheniaceae, as a shaded area. It extends 

 throughout the tropics as a broad belt. But Seward remarks that the absence 

 of Gleichenia from Northern Africa, the whole of Europe, Western Asia, and 

 practically the whole of North America is a surprising fact, to which the 

 geographical distribution of the fossils affords a striking contrast. The 

 recorded Mesozoic distribution of the family is indicated on the same 

 map by enclosed unshaded areas, which show that it then extended 

 widely in N. America and Europe, and even into the Arctic Circle, while 

 the specimens themselves appear closely similar to the living forms. There 

 has then been a notable skrinkage of the area occupied, from the Mesozoic 

 period to the present time. 



The Map B embodies similar results for the Matonia-Dipteris alliance, 

 the living representatives of which are now narrowly restricted to the Malayan 

 region, as shown by the shaded areas. But in Mesozoic times their range 

 was world-wide, as indicated by the enclosed but non-shaded areas on the 

 map. These naturally record only the areas in which the fossils happen to 

 have been collected. The imperfection of the record probably accounts for 

 their isolation. 



The distribution of the Schizaeaceae at the present time is indicated on 

 Map C, by the shaded area, showing that the family now extends throughout 

 the tropics. But again the records of the Mesozoic period indicate that the 

 family then extended northwards into Europe, and into other northern areas 

 where they are not now found. Again the present day area is restricted as 

 compared with that of Mesozoic time. 



A similarly constructed Map, D, relates to the Marattiaceae, of which 

 "the oldest examples of fronds with fertile pinnae agreeing generally in 

 habit with Angiopteris, Macroglossiim, and Archangiopieris are from the 

 Upper Triassic beds of Switzerland, xAustria, and France" (Seward, I.e. 

 p. 235). "It is in the older Mesozoic rocks that we first encounter Ferns 

 which agree closely in habit as also in character of the sori with recent 

 representatives of the family" (Seward, I.e. p. 236). Again this Map shows 



