218 SCIENCE PROGRESS 



water, eaten by birds), Pithecolobiam dulce (eaten by birds), 

 Saccharum spontaneum (wind), Taberncemontana subglobosa 

 (birds), Trema orientalis (by birds). Of the total of 292 vas- 

 cular plants recorded since the eruption, 54 per cent, have 

 probably been introduced by the agency of birds, about 20 per 

 cent, by wind, and about 10 per cent, by water. The order of 

 importance of these three agencies is thus the reverse of that 

 for the revegetation of Krakatau, a difference that is prob- 

 ably to be attributed to the much longer distance of travel. 

 So, too, with respect to the pioneer species, the role played 

 by the lower cryptogams, which in the case of Krakatau was 

 considerable, is here insignificant. 



The lichen Bilimbia artytoides and a few mosses and 

 hepatics attain a limited and local abundance in the damp 

 ravines, but blue-green algae have not been observed. 



J. W. Shive and W. H. Martin {American Journal of Botany, 

 April 191 8) have demonstrated for Buckwheat grown in cul- 

 ture solutions that the optimal requirements of nutrient salts 

 vary with the period of growth. The best growth of both tops 

 and roots up to the period of flowering was found to be 

 KHjPOi, 0-0144 m. ; Ca(N0 3 ) 2 , 0-0052 m. ; MgS0 4 , 0-02 m., 

 whereas the best growth when grown to maturity was obtained 

 with the same salts in the proportions 0-0108 m. ; 0-013 m - 

 and o-i m. respectively. 



In the Journal of Ecology for March 191 8, Dr. W. G. Smith 

 deals with the ecology of Nardus striata and concludes that it 

 is essentially characteristic of the zone marginal to retro- 

 gressive peat where the latter has been redistributed by various 

 agencies. Irrigation, as also manuring, tends to reduce the 

 amount of Nardus present in pasture. 



In the same Journal Salisbury deals with the Quercus 

 sessiliflora-carpinus woods of Hertfordshire and compares 

 them with the woods of that county dominated by Quercus 

 robur. The soils on which Quercus sessiliflora occurs are, in 

 general, lighter, with a lower proportion of mineral salts than 

 those where its congener predominates. 



The ground-flora exhibits several well-defined societies 

 dominated respectively by Pteris aquilium, Rubus fruticosus, 

 Anemone nemorosa, Nepeta glechoma, Mercurialis perennis and 

 Ficaria verna. The last two are particularly associated with 

 areas of low acidity or high water content. In addition, the 



