some Notes on the Leaf-trace in the Ferns. 237 
leaf-trace from which it departs. In the list on pp. 242-5 the species in 
which ‘ reinforcements ’ have been found are marked with an asterisk. 
The nomenclature used in the list is that adopted by Christensen in 
the ‘ Index Filicum \ It has already been stated 1 that, with a few excep¬ 
tions, the same type of pinna-supply is found in the species of a genus, 
recognized as such in the ‘Index Filicum ’. Compared with the total 
number of species named in the ‘ Index Filicum ’ (5,940), the number I have 
examined (220) is very small indeed. But it may be pointed out that 
members of practically every genus with pinnate-leaved species have been 
examined. The exceptions among the species in my list are found in seven 
genera. They would be very much more numerous if other systems of 
nomenclature (e. g. that given in Hooker and Baker’s ‘ Synopsis Filicum ’) 
were adopted. Christensen points out in his preface to the ‘ Index Filicum ’ 
that where possible he has adopted the nomenclature of a monographer of 
a genus. Such a plan has disadvantages as well as very great advantages. 
For the standards of specific distinction (or even of generic rank) adopted 
by the monographer of one genus may be, and most frequently are, very 
different from those of monographers of other genera. It is significant that 
the greatest degree of agreement between the arrangement of species in the 
‘ Index Filicum ’ and that based on the constancy of occurrence of the same 
type of pinna-supply within a genus is found in the genera Diyopteris , 
Polystichum , and Aspidium , of which Christensen has himself made a special 
study. Further, it has been found that frequently where plants placed 
under certain well-known genera like Polypodium or Polystichum have 
a method of pinna-supply different from that prevalent throughout the 
genus under which they are placed (e. g. in Hooker and Baker’s ‘ Synopsis 
Filicum’), they are to be found in the ‘Index Filicum’ under separate 
generic names, often in genera with only a few species. For example, the 
species Phajierophlebia juglandifolia (H. B. Willd.), J. Sm., placed under 
Polypodium in Hooker and Baker’s ‘ Synopsis Filicum ’, has the extra¬ 
marginal type of pinna-supply ; in the species of the genus Polypodium 
recognized in the ‘ Index Filicum ’ and enumerated above, the marginal 
type of pinna-supply prevails. Polystichum viscidulum , C. Chr., has the 
marginal type of pinna-supply ; the extra-marginal type of pinna-supply 
is found throughout the species of Polystichum I have examined; in the 
Addenda of the ‘ Index Filicum ’ Christensen adopts Maxon’s name and 
puts this species in the genus Adenoderris. 
Turning now to the rule of constancy of type of pinna-supply within 
a genus of Ferns in the ‘ Index Filicum ’, we find the exceptions 2 in 
Balantium stramineum (Labill.), Diels. 
Leptochilus tricuspis (Hk.), C. Chr. 
1 Trans. Roy. Soc. Edin., vol. lii, p. 15. 
2 Judging the condition for the genus from that shown by the majority of species examined. 
