484 PROCEEDINGS OF SECTION D. 



2.— A RECORD OF THE GEOGRAPHICAL DISTRIBUTION" 

 OF THE BIRDS OF THE BANDA ISLANDS OF THE 

 ORDERS PASSERES, PICARL^, PSITTACI, AND CO- 

 LUMB^E. ^y J ^ McCLYMONT. 



[Based chiefly on the collections made by Dr. Wallace and by the scientific staff of 

 H.M.S. Challenger. — Ed.] 



3.— ON THE STRUCTURE OF THE LEAF OF BANKSIA 



SERB AT A. 



By A. G. HA2IILT0N. 



[With Four Plates.] 



Among the many adaptations for preventing excessive transpira- 

 tion from leaves, none is so remarkable as the placing the stomates in 

 small cavities or crypts in the under surface of the leaf, these cavities 

 being lined with hairs springing from the interstomatal epidermis. 



One of the best known examples of this is Nerium, oleander ; but 

 in the genus Banksia there are many species which possess this par- 

 ticular adaptation. All the flat-leaved species of this genus that I 

 know have these peculiar cavities, and they are also found in the genus 

 Dryandra. Some of the species of Ficus {e.g., F. rnhiginosa and F. macro- 

 phjlla) have the same structures, but in a much less perfect condition. 



Banksia serrata has flat leaves, the margin coarsely serrate, and 

 the edge considerably thickened. The upper surface is hairless ; the 

 lower shows numerous small white dots about -Imm. in diameter and 

 •1mm. apart, each dot being in the centre of a little square or rounded 

 space, surrounded by the veinlets. These white dots are little bundles 

 of hairs projecting out of the crypts (Plate II.). 



The secondary veins run from the midrib to the margin, and are 

 practically parallel ; they are from 2mm. to 4mm. apart. Between 

 each pair is a smaller -vein, which runs only half-way to the margin, and 

 then divides and is lost in the network of veins filling up the space 

 between the secondary veins. The secondaries fork at the tip, each 

 branch joining those from the veins on either side (Plates II. and HI). 



In texture, the leaf is hard and rather brittle, and the thickened 

 margin adds to the strength and stiffness of the blade. 



The young leaves are soft, but are protected from heat and drying 

 winds by a thick coating of long, straight, rusty or fawn-colored hairs 

 (Flate I., figs. ] and 2). These are shed as the leaf matures. The 

 hairs are shortly articulated and very thick walled, the cavity being very 

 narrow and usually filled with air, although at times there are brown 

 contents. Sometimes they are irregularly constricted (Plate I., fig. 2). 

 On the midrib and margin there are hairs of the same character, but 

 shorter, and twisted like corkscrews (Plate I,, fig. 3), and the midrib 

 also bears a few very long straight hairs — quite three times as long as 

 the ordinary straight ones. 



