MERIDIANS OP DISTRIBUTION. 



47 



The Japan-Cbina-Himalaya meridian of distribution exhibits the most striking 

 predominance of red throughout, and it deserves to be noted that if the species enden 

 m the two Arctic peninsulas 1 that project towards this meridian be subtracted from the rest of 

 the Arctic species, the circumpolar colour percentage becomes—yellow, 66'7 ; red, 33^, 



a result in accordance with the evidence from endemic percentage and structure' ' 



The predominance of red, so marked along the Japan meridian even from within the 

 Circumpolar province, and culminating in the Himalaya in the overwhelming proportion 

 of 79 red to 21 yellow, has some striking features within the last-named province. In 

 the West Himalayan division (Trans-Indus, Panjab Himalaya, and Kamaon districts) 



where there are altogether only 23 species— 9, or 39 per cent., are yellow. This is in 



marked agreement with the percentage for Tibeto-China, the slight preponderance o* 

 yellow over the average Chinese percentage being perhaps due to the influence of the 

 adjacent meridian of distribution. In the Eastern Division (Nepal, Sikkim, and Chumbi) 



e 



there are 50 species, of which only 8, or 16 per cent., are yellow, while in the 

 Indo-Chinese division (Assam, Burma, Yunnan) there are 47 species, of which 5, or only 

 10*8 per cent., are yellow. The condition along this meridian is thus more striking 

 and more uniform than even the diagram indicates. 



One other general character— that of phyllotaxis — remains to be considered. W 

 have seen that the leaves in this genus may be alternate or may be opposite, and although, 

 for reasons which have been already explained, the use of this character in a primary subdivi- 

 sion of the genus has been abandoned, the character is nevertheless a highly natural one. 



■ 



There is the same difficulty in estimating the value of the character here as there 

 was in using it for purposes of classification. It affords from internal evidence no clue 

 to its own evolutionary history. "We are unable to gather from morpMogy whether 

 the alternate- leaved or the opposite-leaved condition is the more archaic. 



The alternate-leaved condition prevails, as we have seen, in the proportion (roughly) 

 of 65 : 35. But we have seen also that its general relationship to structure is one of 

 indifference, and we know that of the Tribe EUPHRASIES, to which the genus belongs, 

 and of which it certainly does not exhibit the most archaic type of corolla, an opposite- 

 leaved condition is highly characteristic. Its relation to structure in particular sections* 

 is not more instructive. If the Siphonanth^— " nobilissimae et omnibus reliquis ante- 

 ponendse m — are alternate-leaved, the Orthorrhynchjs, which contend with these for the 

 hegemony of the genus, are as characteristically opposite-leaved. Rhyncholoph^e are 

 mostly alternate-leaved, it is true, but there are some of the groups that were included 



the abandoned « Verticillataa " that have Rhyncholophous corollas. Then Bidentat^. 

 of which till quite recently alternate-leaves were supposed to be characteristic, are 

 not only being reported in constantly increasing numbers from the Eastern Himalayan 

 divisions with opposite leaves, but the highest degree of specialisation on this particular 

 line of evolution (shown by the LyraUe) is concomitant with the possession of opposite 

 leaves. As regards Anodont^e, which exhibit the most archaic types of corolla, the 

 balance is in favour of opposite leaves, the proportion of these to alternate being at 

 present 35 : 27, but the evidence is too slight to be conclusive. ^ 



The following diagram on this account affords no assistance in considering the question 

 of general distribution. In this case indeed the evidence obtained elsewhere is required to 

 explain the character that the diagram illustra tes. In details, however, and as re jirdu 



* P. nasuta in Kamchatka \^J^^^^ both of which « without close structural 



allies elsewhere in the Circumpolar Flora and both of which hare red corollas. 



in 



' Maxiniowicz, Mel. Biol, xii, 778. 



