:\IK1{T.STJC FLOKAL VARIATION ITs GALlE.li 



231 



botanists may name plants, but to study and correlate the characters 

 .and affinities o£ different groups, even though certain characters may 

 be practically worthless for purposes of determination. The study of 

 mei-istic variation, for instance, is hardly a j^ractical method of deter- 

 inining a species, though, in cases of two or more species whose 

 independent status is in question, a knowledge of their respective 

 meristic variation would be valuable in deciding their claims to specific 

 rank. 



Natural groups of plants may be either homomeristic or hefero- 

 meristic, A homomeristic group is one in which all the subordinate 

 groups have the same floral formula, e. g., Compositce, JJmheUiferce 

 (excluding the gynseceum). A heteromeristic group is one in which 

 the subordinate groups have floral formulas which differ numerically, 

 e. g. OnagracecB, Bubiacew, Frlmulacece. 



It may be assumed that variation in the number of parts is more 

 likely to occur in heteromeristic groups than in homomeristic ; the 

 fact of a group being heteromeristic shows that a change in the 

 number of parts has occurred in the past, and the tendency to chano-e 

 may well persist in the form of meristic variation. 



Allomeristic groups are such as differ meristically from a majority 

 of related groups, e. g. Potentilla evecfa Hampe, which is tetra- 

 merous in contrast with most other Potentillas which are pentamerous. 

 Similarly Veronica has a 4-lobed corolla, whereas most other scrophu- 

 lariaceous geneiu have 5-lobed corollas. Meristic variation is naturally 

 more prevalent in allomeristic groups than in isomeristic, Pentamerous 

 and trimerous flowers are not infrequent in Potentilla erecta, and 

 great meristic variation has been observed in Veronica jjersica Poir. 

 (Penzig, Pflanzenteratologie, i. 433; ii. 212). 



The family Buhiaccw is heteromeristic, the number of corolla - 

 lobes ranging from 4 to in the Nauclece and 4 to 10 in the Guet- 

 tardew and Ghiococcece. The tribe Galiece is also heteromeristic. 

 In Bentham and Hooker's Genera Plantarum eleven genera are 

 included in this tribe of which Buhia and Fliuopsis are described as 



Percentages of flowers of different types. 



