556 SCIENCE PROGRESS 



more geological periods. A fauna or flora may therefore 

 advantageously be correlated as belonging within the limits 

 of a certain environment independent of stratigraphic levels. 



The Gatooma country (S. Rhodesia), as described by 

 A. E. V. Zealley and B. Lightfoot, consists of quartzites, banded 

 ironstones, and greenstones, into which large batholiths of 

 granite and numerous masses of quartz-porphyry have been 

 intruded (Geol. Surv., S. Rhodesia, Bull. No. 5, 1918, pp. 68). 

 Gold is the chief mineral product, and is found in replace- 

 ment deposits of gold-bearing sulphides disseminated in fissure- 

 zones, and in fissure veins of gold-bearing quartz. Antimonite 

 and scheelite are also found. In a further paper Zealley 

 demonstrates that the rocks in the Gatooma area, hitherto 

 known as " banded ironstones," are really ferruginised and 

 silicified ielsites and quartz-porphyries (Trans. Geol. Soc. 

 South Africa, 191 8, 21, 43-52). 



Dixey, F., and Sibly, T. F., The Carboniferous Lime- 

 stone Series on the south-eastern margin of the South Wales 

 Coalfield, Quart. Journ. Geol. Soc. 1918, 73, pt. 2, 1 1 1-64. 



Trechmann, C. T., The Trias of New Zealand, ibid., 

 1918, 73, pt. 3, 165-246. 



Marshall, P., Geology of the Central Kaipara (New 

 Zealand), Trans. New Zealand Inst. 191 7, 49, 433-50. 



Emerson, B. K., The Geology of Massachusetts and Rhode 

 Island, U. S. Geol. Surv. Bull. 597, 191 7. 



Hawkins, A. C, Notes on the Geology of Rhode Island, 

 Amer. Journ. Sci. 191 8, 46, 437-72. 



Powers, S., Notes on the Geology of Eastern Guatemala 

 and North-western Spanish Honduras, Journ. Geol. 191 8, 26, 



5 7-23. 



BOTANY. By E. J. Salisbury, D.Sc, F.L.S., East London College, 

 University, London. 



Anatomy. — The aerenchyma of Epilobium hirsutum has been 

 studied by Miss L. Batten (Journ. Ecology, Nov.), who finds 

 that it is developed from the phellogen in May and that its 

 development depends on external conditions. The aerenchyma 

 arises within the endodermis and may consist of a loose tissue 

 of irregularly arranged rounded or radially elongated cells, 

 or of concentric zones separated by air spaces and bridged by 



