BRITISH SPECIES OF THE GENUS MNIUM. 43 
TasLE XVII. 
Description of Mnium hornum, Linn. 
A.—Specific limits of variation. 
[6 localities in Great Britain. | 
l. Length of the leaves: 5:17-8:06 mm, 
2. Breadth of the leaves: 0:64-1:46 mm. 
3. ie is 5 at their base: 0°55-0°98 mm. 
4. 5 » cells: 14-20 pg. 
5. Number of cells: 34-73. 
6. Breadth of the border of the leaves (often recurved): ?. 
7. Number of cells of the border (often recurved, see § 30): ?. 
8. 2 marginal teeth: 46-84. 
9. = double (and triple) marginal teeth : 34-61. 
10. Teeth on the nerve at the back of the leaf: 4-9. 
Length of the nerve: nerve reaching the summit (4-), ceasing below the summit 
= 
[zr 
( —), or intermediate form (+). 
12. Tooth at the summit of the leaf: always existing. 
13. Number of leaves: 46-64 (perhaps more, as many as 80 ?—See § 23). 
14. » fruits: always 1. 
bo 
B.—Gradation of the characters. 
[One patch: Dungeon Ghyll, Lake District, 8 stems. ] 
Mean interval curves. 
Intervals : i 2. 3. 4. 5. 6. a 8. 9. 10. 
Length leaves (mm.)...... 200 200a 900 aes 9/70. 428) 405 524 6:01 6779 
Breadth leaves (mm.) .... 0:53 0°63 074 0:991 111 1:26 1832 1:41 143 118 
o bsimm.)-.....-. 0:50 O2 OG (i68. 0:74 0708:0777 OBI 085 084 
EB NN... p. NEU C de. 1005 03:7 4. des "18 
INIIDONGBlNS si eee reni 85 gp D bo: 00 oam oao TA — 72. OS 
Breadth border .......... p 
COL DOTAN, use rris F Ri E : T i ipf TE e. a 
Marginal teeth .......... 1:5 3 10 23 35 42 49 55 DD. Of 
Double marginal teeth .. . O1 L3 4 WS: 98. 808 8D AI 48. 48 
lleoth;nerye. ...de eser 0 0 EDAM  q0 94: mU 04 76 9 
length nerye*........... — +- - — — t- +- +- +- +- 
Bob minmit......:-..-- T ete CL dubio qub c d dE 
* In the intervals 1-8 all the leaves were —, except: 1°, in each of the intervals 2, 7, 8, 
one leaf +; 2°, in interval 6, one leaf +. 
