RECENT ADVANCES IN SCIENCE 391 



Gaz. July), and in the same journal M. C. Bliss deals with 

 the interrelationships of the Taxineae. 



P. Vuillemin (Comptes Rendus) treats of the interrelation- 

 ships of the Incompletes (Amentales), which are held to be 

 primitive, and their connection with the higher plants. Both 

 the Hydnoraceae and Nymphaeaceae are regarded as related 

 to the Piperaceae. 



Ecology. — Prof. Herdman has studied the plankton diatoms 

 of the Irish Sea {Jour. Linn. Soc. No. 297), which consist 

 mainly of members of the genera Biddulphia, Chcetoceras, 

 Coscinodiscus, Rhizosolenia, Thalassiosira, Guinardia, and 

 Lauderia. The first named is represented by two species, 

 viz. B. mobiliensis and B. sinensis, which appear from September 

 to June, with a maximum development in March or April, and 

 a secondary maximum in November. Coscinodiscus is repre- 

 sented by several species, which likewise attain their greatest 

 abundance in March or April. Chcetoceras , represented by a 

 number of species, exhibits two maxima, viz. a primary in April 

 and a secondary in September. Lauderia borealis is most abun- 

 dant at the end of April, and the species of Thalassiosira from 

 then onwards till the end of May. Both Rhizosolenia spp. and 

 Guinardia flaccida are late diatoms with their maximum in 

 June. 



J. B. Pole-Evans, in The Official Year Book for 191 7, gives 

 an excellent little summary of South African vegetation. This 

 is accompanied by a map showing the geographical distribu- 

 tion of the chief types of plant communities and beautifully 

 illustrated with some forty-eight half-tone plates. 



Pedigree cultures of oats have been grown by J. O. Dickson 

 in quartz sand, with culture solutions having identical osmotic 

 concentrations, but deficient in either magnesium, calcium, 

 potassium, phosphorus, or nitrogen {Am. Jour. Bot. June). 

 The general development was most adversely affected by 

 deficiency in phosphorus or nitrogen, but the absence of 

 magnesium or calcium increased the vigour of growth, though 

 diminishing the production of grain. The water supply neces- 

 sary for maximum growth decreases when there is a deficiency 

 of magnesium, whilst it is increased by a deficiency in calcium, 

 and still more when there is an inadequate supply of potassium, 

 phosphorus, or nitrogen. 



Two papers of considerable interest, both to the ecologist 



