66 TRANSACTIONS OF THE [Skss. lxxx 



is unilateral, filling the space between the three small petals 

 and the ovary which it embraces. Its median is therefore 

 opposite the gap between the two petals Avhich are or may 

 be enlarged. It increases the irregularity of the flower 

 and is an evident feature, covered as it is by more or less 

 prominent tubercles. In all the other species — so far as I 

 have been able to examine them for the character — the disk 

 is circular and completely encircles the ovary, at the same 

 time showing a smooth surface with at times faint evidence 

 of tuberculation. How far the character of the disk can 

 be used for specific distinction and grouping, investigation 

 will show. 



The fruit character of the Diptera Saxifrages is one of 

 much interest to students of adaptations. As the gynaeceum 

 enlarges the pedicel at a point immediately below the torus 

 shows curvature and always in direction towards the 

 posterior side of the flower. The curvature proceeds until 

 the developing fruit becomes inverted with one septal 

 surface closely adpressed to the pedicel. This curvature 

 brings at the same time the large anterior j)etal, which has 

 been enlarging and stifiening, from its downwardly directed 

 position as a hanging flag in the flower into an erect or 

 nearly erect position on the curved end of the pedicel and 

 above the upward turned base of the fruit. We get ^hen 

 a capsule with mouth directed downwards — the mouth being 

 a transverse slit between the styles, the size of which can 

 be regulated by the degree of drying of the style-bases— 

 surmounted by an erect stifl' strap-shaped petal one or more 

 centimeters long. There may be two such j^etals. The 

 mechanism may be interpreted in terms of seed-distribution, 

 and the suggestion is an obvious one that the petal, exposing 

 a surface to currents of air, is the agent through which 

 vibration is communicated to the stifl" tln-ead-like pedicel 

 below, and the seeds protected from wet in an inverted 

 capsule are shaken out easily from the downwardly directed 

 capsule mouth. 



The J/iptera Saxifrages are all Japanese or Chinese — 

 China claiming nine, and Japan five. One of the Japanese 

 species — >S'. sarmentosa, Linn. fil. — has been sent in dried 

 specimen from China, but it is a doubtful native. 



