122 THE JOURNAL OF INDIAN BOTANY. 



infinitesimal fraction of the plants that he sees around him. Of that 

 fraction many are simply freaks or sports ; and as there is a tendency 

 for such freaks to he collected and to find their way into herbaria 

 it follows that herbaria may often give an exaggerated impression of 

 the range of variability of species generally. Into the genetic phe- 

 nomenon of freaks this paper cannot enter. 



Over and above freaks we have to recognize a number of other 

 types of variability. 



First there is the phenomenon of geographical change, which 

 may be either gradual or sudden. As an example of the first, the 

 colour of the spikelets of many Cyperacece and GraminecB is paler in 

 North India and gradually darkens as one goes south, until on the 

 Nilgiris it is almost black. As an example of the second, Ageratmn 

 conysoides Linn, is on the Nilgiris a delicate-stemmed plant with pure 

 mauve flowers, while in the Dharwar District of the Bombay Presi- 

 dency it is a coarse-stemmed and coarse-leaved plant with dirty white 

 flowers. The causes of geographical change are very obscure. Complex 

 climatic factors have to be reckoned with, as well as geological for- 

 mations. There is also the phenomenon of isolation of " lines, " which 

 are discussed below. 



Secondly there is a type of variability of a purely edaphic character 

 within the same geographical region. Thus Flueggea hucopyros Willd. 

 would seem to be merely an edaphic (xerophytic) form of F. 

 microcarpa Bl. ; Leucas Montana Sr. would seem to be the xero- 

 phytic form of L. mollissima Wall. Ihe various edaphic forms of 

 many species not hitherto split off by the Floras are well known. 



Thirdly there are distinct cases of variability in life-period. Thus 

 Fimbristylis diphylla Vahl., a perennial, has an annual form var. 

 annua (sp.) R. and S. : and similarly Cypents Iria L. (see p. 693 

 of Journ. Bom. Nat. Hist. Soc. Vol. XXV No. 4). Cypcrus fiavidus 

 Retz. would seem to be only an annual form of C. Haspan L. 



Fourthly there would seem to be plants which exhibit a sort of 

 seasonal dimorphism, not of course homologous with the same pheno- 

 menon in insects. Thus some species of Smithia have small flowers 

 when they mature in the rains and large ones when they mature in the 

 dry weather. S- flava Dalz. (var. in Cooke. F. Bom. Pres.), if not 

 a valid species is apparently a seasonal form of S. sensltiva Ait. ; while 

 last winter the writer found at Yellapur in North Kanara a plant 

 which corresponded exactly with S. bigemina Dalz. except that it 

 was much larger in all its parts especially the flowers, and had matured 

 in the winter instead of the rainy season. 



Fifthly there is the much more difficult phenomenon of " lines ". 

 That these are due to the interplay of Mendelian characters is now 



