1915-16.] BOTANICAL SOCIETY^ OF EDINBURGH 65 



Saxifrages of the Diptera Section, with Description 

 OF New Species. By Professor Bayley Balfour, F.R.S. 



(Read 7th ()ctober 1914.) 



The Diptera Saxifrages — we know something of four- 

 teen species — form a compact group marked b}'' peculiar 

 distinctive characters of flower and fruit. 



Those of the corolla are the most striking. The petals 

 are unequal. The anterior petal is alwaj^s the longest and 

 from a shortly clawed base elongates to strap-shaped form 

 and appears like a wing hanging from the front of the 

 flower which is usually placed on the inflorescence with 

 its axis horizontal. This anterior petal is persistent and 

 enlarges during fruiting, becoming at the same time some- 

 what stifl". One of the antero-lateral petals, that towards 

 the left, is sometimes similarly enlarged, the enlargement 

 being equal in amount, or perhaps more often slightly less. 

 The other petals are also unguiculate but are muph smaller, 

 sometimes not a fifth the length of the larger one or ones, 

 and they fall ofl" early. The petals all have a white ground- 

 colour — save in S. He7iryi, Ball fil. in w^hich Henry says 

 the flowers are red — and the long petals do not show much 

 blotching ; that is reserved for the smaller petals in several 

 species where they are yellow and red-spotted. The flowers 

 in these Saxifrages are then irregular, and it is the presence 

 of these long petals hanging in front of the flower that 

 gave Borkhausen his generic name. 



In one species, S. cuscittaeformis, Lodd., the petals have 

 been described and indeed figured as having all the elongated 

 form characteristic of one or two petals in other species. 

 In the plants of this species which have flowered at Edin- 

 burgh this equality of petals occasionally^ appears; as a 

 rule the flowers show only slight divergence towards 

 equality. 



The large yellow disk is a marked feature in the Section 

 and requires further examination in fresh material of several 

 species. In some — for instance, S. sarmentosa, Linn, fil,, 

 S. cuscutaeformis, Lodd., S. Veitchiana, Bali. fil. — the disk 



TRANS. BOT, SOC. EDIN. VOL. XXVII. 5 



