193 



THE EXTREME HARDNESS OF THE SEEDS 

 OF CAESALPINIA DIGYNA. 



In 1910, the writer obtained two dozen seeds of Caesulpinia 

 digyna, Rottl., from Burma, intending if possible to isolate on them 

 the water-resistent layer which hinders the germination of quite a 

 number of the Leguminosae, such as Acacia arabica and various 

 indigos. The intended study was never completed; but observations 

 were made on the resistance of the seeds to germination. 



The seeds were placed half-submerged in clean water, which was 

 frequently chansied, but none germinated during nine months ; 

 next they were allowed to dry and after about three months out of 

 water, they were placed in it again half-submerged as before; still 

 there was no germination. A few were removed from the experi- 

 ment to see if they were alive ; they were cut slightly so that the 

 impervious layer was broken, whereupon they all germinated. The 

 remainder passed another six months half-submerged, but did not 

 germinate ; then they passed a year dry. Half-submerged again for 

 the third time, as before they did not germinate during two months. 



It seemed probable after this that the alternation of wet and 

 dry seasons such as occurs where the plant chiefly grows, has 

 nothing to do with the germination. However, it was thought that 

 perhaps jungle-fires might bring it about ; and ten seeds were accor- 

 dingly placed under a layer of dry leaves prepared to produce a 

 flame a foot high, which was fired ; the seeds, when the fire had 

 passed from them, were collected and replaced again in water, they 

 still did not germinate until they were cut. With this the experi- 

 ments ended, the supply of seeds being exhausted ; but the living 

 plants now in cultivation in the Economic Garden, Singapore, are the 

 offspring of these seeds. 



It seems as if Caesalpinia digyna only germinates after direct 

 injury to the outermost layer of the seed-coat. 



Several years ago Professor W. R. Dunstan, Director of the 

 Imperial Institute, London, showed what splendid leather is produced 

 by tanning with the pods of this plant, but a barrier to its use was 

 found in the high cost of collecting them from the bushes which grow 

 too scattered. Should it ever be possible to bring the pods into the 

 market, it is most likely to be by encouraging the plant to grow 

 thicker by sowing prepared seeds in waste places. 



I. H. BURKILL. 



A DISEASE OF AGAVES. 



There is a disease on Agave plants in Singapore, and in the 

 state of Johore, due to a fungus. This fungus attacks the mature 

 leaves on the upper surface, rendering them valueless for the 



