720 



TRANSACTIONS OP SECTION K. 



(6) Between the leaves of several stems of the same species (by comparing the 

 leaves which belong to the same interval in all the stems) ; 



(c) Between the leaves of several species of the same genus (same method as 

 for b). 



We are also enabled to study more accurately the ordinary variability of a given 

 character among individuals of the same species, by comparing the leaves of the 

 successive intervals I, 2, .... 7i of several specimens. 



The description of a species, according to my method, consists of a certain number 

 of tables giving the period of each character, the figures being based as far as possible 

 on specimens from several localities. I have studied Mnium caispidahun, M. Jiornum, 

 M. punctatum, M. rostratimi, M. serratum, M. suhglohosum, M. undulatum ; for each 

 species the following characters were taken : Length, breadth, breadth at the base, 

 number of cells and breadth of the cells at the place of the greatest breadth, breadth 

 of the border and number of cells of the border at the same place, number of teeth 

 at the border and on the nerve, length of the nerve (reaching the summit or Jiot), 

 tooth at the summit of the leaf (present or absent), total number of leaves of the 

 . fertile stem. 



To make the identification of a given specimen easier, we may use tables giving 

 the minima] and maximal values of each character for the leaves of the 10"' interval 

 (longest leaves) only. The following Tables are of this nature : — 



Table 8 (mm.). 

 Length, minimum. 



Serratum 2.91 



Guspidalum 3.73 



Subglobosum 4.45 



Bostratum 4.90 



Hornum 5 "42 



Punctatum 5.75 



Undulatum 6.93 



Table e (mm.). 

 Length, maximum 

 Serratum 

 Cuspidatum 

 Subglobosum 

 Hornum 

 Bostratum 

 Pimctatum 

 Undulatum 



4.53 

 4.68 

 7.06 

 7.49 

 8.32 

 9.21 

 11.61 



Table ( (mm.). 

 Breadth, minimum. 



Serratum 0.72 



Hornum 0.87 



Cuspidatum 1.29 



Bostratum 1.80 



Undulatum 1.82 



Punctatum 2.77 



Subglobosum 3.05 



Table v (mm.). 

 Breadth, maximum. 



Serratum 1.27 



Hornum 1.38 



Cuspidatum 1.88 



Undidatum 2.35 



Bostratum 3.19 



Subglobosum 5.50 



Punctatum 6.48 



For example, on using the Tables S-r;, we take the longest leaf of a fertile stem 

 and obtain the following measurements : Length 5.64 mm., breadth 2.15 mm. Let 

 us try to identify the species by means of the tables : 6 excludes undulatum (and 

 perhaps punctatum); e excludes serratum and cuspidatum; C excludes punctatum 

 and subglobosum ; v excludes serratum, cuspidatum (both already excluded), and 

 Jiornum. The stem thus belongs to the species rostratum. 



In this example it was possible to find the name by two characters ; of course, we 

 shall often be compelled to make use of three or more characters. As we have at our 

 disposal a dozen of characters, we may hope that the identification of a given specimen 

 will be always possible, even if the species to be considered were more numerous, the 

 specific tables of the periods allowing verification. 



2. The A'piian Flora of Brlialn : Early Angiospenns and their Contempo- 

 raries. By Dk. Mabie C. Stopes. 



The so-called ' Lower Greensand ' deposits of this country are of Aptian 

 age, and represent the upper division of the Eorretaccous according to the 

 recent classification of Haug. From these deposits the ijlauts hitherto known 



