BOTANY 215 



cent., Greaves and Carter have determined the effect of varia- 

 tions in the soil moisture and salt content on bacterial activity. 

 The greatest ammonifying power was exhibited at a water 

 content of 30 per cent., and in the presence of carbonates this 

 value remained, but when magnesium sulphate was present 

 the optimum condition was 25 per cent. The maximum nitri- 

 fying power was exhibited at a water content of 20-30 per cent., 

 the value varying with the nature of the salts present. It is 

 important to note that the relative toxicity of various salts to 

 nitrifying organisms decreased as the amount of water added 

 increased {Soil Science, vol. xiii, pp. 251-70). 



The effect of tree products on Ammonification and Nitri- 

 fication has been studied by Gibbs and Werkman {Soil Science, 

 vol. xiii, pp. 303-22). It was found that Fir needles depressed 

 the ammonification by about 25 per cent., but Larch needles 

 and Bracken litter caused very slight depression. 



Nitrification of ammonium sulphate was depressed by all 

 types of litter, even 3 per cent, of Bracken litter causing a 

 diminution of over 25 per cent., whilst the needles of Abies 

 grandis, Pinus ponderosa, and Thuja plicata almost totally 

 inhibited the process. 



A summary of the results of experiments on the viability 

 of buried seeds, initiated by Dr. Beal in 1879, is furnished by 

 Darlington {Am. Journ. Bat., vol. ix, p. 268). The seeds were 

 placed in uncorked bottles and buried with the opening directed 

 downwards. Twenty samples each of fifty seeds were buried, 

 and this was done for twenty-three species ; mostly common 

 weeds. After forty years Brassica nigra and Riiniex crispus 

 exhibited a percentage germination of 18 and Plantago major 

 10 per cent. Amarantkiis grcecizans yielded no less than 66 

 per cent., and CEnothera biennis 38 per cent. Other species 

 which had survived were Amaranthns retroflexus, Ambrosia 

 elaiior, Lepidiiim virginicum, Portidaca oleracea, and Chenopo- 

 dinm album. Capsella bitrsa-pastoris germinated after thirty-five 

 years, but failed to do so after forty years. Since, however, 

 such a failure with this species occurred also after ten years, 

 the recent result may have little significance. 



Taxonomy. — A new genus of Umbellifer^ allied to Hydro- 

 cotyle is described by Norman under the name of Cotylonia 

 {Jour. Bot., vol. ix, p. 166). Dr. Schonland {Ann. Bolus. Herb., 

 Dec. 1 921) has described a new genus of Crassulaceae to include 

 a single species, Pagella archeri. Its outstanding features are 

 the markedly syncarpous ovary associated with a haploste- 

 monous tetramerous flower and the presence of two separate 

 placentas in each loculus. The largest plants are about 

 2Q mm. in diameter. 



A new species of the interesting genus Brachiomonas under 



