Edu o 
See ee a i eee Oe 
24 PROF, JULIUS MACLEOD ON TEN 
occurs again and again, and it seems to be insuperable. There are, however, 
three methods to surmount it. 
The FIRST METHOD consists in trying a second character of the same 
specimen æ : for instance, the breadth of the longest leaf, which is in our 
example 1:93 mm. On the other hand, the limits of the breadth are in the 
two species : 
E Oumtdatum- Dove ee 1:29 mm. 3:26 mm. 
LIST s 1127 ABUSE IRSE E ets 004 5.35 1:446. 
Although the two specific curves are again overlapping each other, 
hesitation is no longer possible : æ is cuspidatum. 
In the above example, two measurements allow us to identify 2 *. 
According to my experience with Carabus and Mnium, this happens more 
frequently than one would think. It is, of course, often necessary to 
measure more than two characters of a specimen, especially when we 
want to make a choice between numerous species. 
The SECOND METHOD is applicable when we have at our disposal two or 
more specimens which belong with certainty to the same species, This is the 
ordinary case with Mosses, as several stems of the same species are to be 
found in one patch f.— Example: In a patch w, the breadth of the longest 
leaf of four fertile stems was measured ; the figures were 
1:19 mm. 1:15 mm, 0:05 mm. 0:67 mm. 
Comparing the specific limits given above, we see that the first figure 
(1:19) is doubtful ; it points to hornum, but the difference between 1:19 
and the minimum of cuspidatum is too small to give a decision. The second 
figure (1:15) is also doubtful, but the two figures together make it probable 
that the patch æ is hornum. The third and the fourth figures (0°95 and 
0°67) are decisive in favour of hornum ; the four stems (and the whole 
patch 4) belong thus to this species. 
The principle of the second method is that, in a series of specimens which 
certainly belong to the same species, the identification of al/ the specimens 
is possible if one of them gives a decisive figure—even if the figures of all 
others are not decisive. 
The THIRD METHOD is applicable if one specimen affords opportunity of 
measuring a given character two or several times. 
In the above example of application of the first method we limited ourselves 
to the measurements of the longest leaf of the fertile stem æ which we wanted 
to identify ; but we may go further, and take all the leaves of the tenth 
interval of z ($ 12, Remark II.). The number of those leaves depends, of 
course, on the total number of leaves of the stem, as one sees in Table XIII. A. 
* If we had taken at first the breadth, one figure would have been sufficient. 
T It is, of course, necessary to ascertain that the patch is homogeneous. 
