10 WILLIS : EVIDE.NCE AGAINST THE ORIGIN OF 



These two species must have had a conitnon not very remote 

 ancestor, and as the main differences are in number, the 

 variation must have been discontinuous. 



The same kind of arguments may be used here as in the 

 case of Coleus elongatus. Are we to suppose the conditions 

 of Hfe so different in the Ceylon and Indian mountains that a 

 5-petalled flower will suit the one, a 12-petalled the other ? 

 Or how is the one to pass into the other, or both to arise from 

 a common ancestor, except by discontinuous variation ? 



The next genus in which local endemics occur is Acrotrema, 

 and these differ mainly in the shapes of the leaves. Can it be 

 supposed that the simple obovate-lanceolate leaf of A. inter- 

 medium fits it for the Kitulgala district, while the pinnate 

 leaf with linear-lanceolate segments of A. Thwaitesii fits that 

 species for the Dolosbage district, but a few miles away, a 

 trifle liigher up , and in a similar climate ? The only species of 

 this genus that is at all common is A. uniflorum, which occurs 

 in a great variety of forms, " almost every district producing 

 a local form " (Trimen). A. lyratum, characterized by very 

 long peduncles, is found only on the summit of Nillo wekanda , 

 an isolated precipitous rock in the Hinidum pattu ; its nearest 

 relative appears to be some form of A. uniflorum, found in the 

 district, but not actually recorded for Nillowekanda. Now, 

 is it to be supposed that the long peduncles are any advantage, 

 or that the struggle for existence on the summit of Nillowe- 

 kanda is so keen that they can have been evolved there by 

 infinitesimal variation ? 



Or , again,inSchumacheria, why should the oval or rotundate 

 leaves of S. alnifolia be suited to Ambegamuwa, &c. , while the 

 lanceolate-oblong leaves of S. amjustifolia are suited to the 

 Kukul korale i 



Why, again, should Dillenia retuso. with its obtuse leaves 

 and small flowers, be found alongside of D. indica, with its 

 acute leaves and large flowers ? Both are common in the low- 

 country of Western Ceylon, while in Western India D. indica 

 occurs witli D. hracteata, a still nearer relative of D. retusu. 



