VARIATION— GENERAL RESULTS. 



21 



Schenk ('86) , in his well-known " Biologie der Wassergewaechse, " gives 

 the number of leaves to the whorl as between 6 and 10, but no special 

 weight is to be given to this statement, as it is clear from internal evi- 

 dence that his account of Ceratophyllum is very largely taken directly 

 from Schleiden. Strasburger (:02), in his recent memoir on Cerato- 

 phyllum, says (p. 486), regarding the number of leaves to the whorl: 

 ''In den mir zur Verjiigung stehenden Exemplaren von Ceratophyllum 

 submersum war die Zahl der Blatter in den Quirlen sehr haufig zehn." 

 Further references to the literature regarding this matter are unneces- 

 sary. The point I wish to bring out is merely that so far as we can 

 judge from such very slender evidence, the condition of Ceratophyllum 

 with respect to number of leaves in the whorl in European countries 

 (Germany and Sweden) is apparently not very widely different from 

 what it is in America. 



Table 3. — Coefficients of variation in plants. 



The relative degree of variation in this character of Ceratophyllum 

 as indicated by a coefficient of variation of about 14 per cent is of the 

 same order of magnitude as that which Pearson (:01) has found for a 

 variety of characters in different plants. In his table xxxiv (loc. cit. , 

 p. 361) are given the coefficients of variation for 26 cases, covering a 

 wide range of plant forms and characters. These coefficients of varia- 

 tion range between 7.80 and 41.96, with a mean of 19.97. Our value for 

 Ceratophyllum leaves comes very close to the coefficient measuring 

 variation in the stigmatic bands of Shirley poppies, for example, or to 

 that for the veins in the leaves of Spanish chestnuts. In order that a 

 comparison may be made between other well-known biometric results on 

 variation in plants and what we have found for Ceratophyllum, a table 

 of coefficients of variation (table 3) has been prepared. 



