370 SCIENCE PROGRESS 



55 occur in the upper plaisancien of St. Marcel. Of this total 

 47 are probably living species, and 26 constituents of the 

 existing flora of the region (e.g. Populus tremula, Quercus 

 sessiliflora, Castanea vesca, Buxus sempervirens) , its Mediter- 

 ranean element is exemplified by Quercus lusitanica, Platanus 

 orientalis, Ilex balearica, Neriuni oleander^ etc. 



A North American element is presented by Juglans cinerea, 

 Liriodendron tulipifera, Sassafras officinale, and Sequoia semper- 

 virens, whilst the Canary Island flora is represented by Laurus 

 canariensis, Celastrus cassinoides. Ilex canariensis, Persea indica, 

 and Oreodaphne foetans. The flora of the East is also repre- 

 sented by Torreya nucifera, Glyptostrobus heterophyllus , Ginkgo 

 biloba, Quercus serratus, Buettneria aspera, and species of 

 Cinnamomum. From a consideration of the present require- 

 ments of these species the author concludes that the climate 

 at that period was probably comparable to that of the southern 

 part of the United States. Several of the fossil species are 

 identical with those of the cretaceous in Greenland and of the 

 eocene deposits in the Paris basin. It is suggested that these 

 indicate a southern emigration. 



Matthews has made a study of the Perthshire flora from the 

 point of view of the age and area hypothesis {Ann. Bot., vol. 

 xxxvi, pp. 322-7), and finds it to be generally applicable to 

 a county flora, though, as was to be expected, the relic arctic- 

 alpine flora does not conform to the general principle. 



Cytology. — Heilborn, in a brief paper on the chromosome 

 number in the genus Carex {Svensk. Bot. Tid., pp. 271-4, 1922), 

 corrects some earlier observations, and adds data respecting 

 other species which show the great variability of chromosome 

 number within this genus. There appear to be 9 chromosomes 

 in Carex pilulifera ; 1 5 in C. ericetorwn ; 1 5 or 1 6 in C. vaginata ; 

 16 in C. panicea ; 19 in C. montana ; 26 in C. digitata and 

 C. dioica ; 27 in C. atrata ; 28 in C Halleri ; 31 in C caryo- 

 phyllea ; 32 in C pallescens ; 34 in C. vulpina ; 35 in C flava ; 

 36 in C. riparia ; 35 in C. rostrata ; 40 in C. caespitora and C. 

 Hudsonii ; 41 in C. vesicaria ; 42 in C. gracilis and C. Goodenovii. 

 It would seem, therefore, that the chromosome number bears 

 no relation to the taxonomic affinity, for whilst closely related 

 species {e.g. C. pilulifera and C. montafia) may have very different 

 chromosome numbers, two such very widely separated species 

 as C. dioica and C. digitata have the same number. 



To the list of plants in which cell division of the 

 Angiosperm microspore takes place by furrowing, in place 

 of cell plate formation, C. H. Farr has added Nelumbo 

 lutea. The fact that this type of division has also been 

 found in Nicotiana, Primula, Tropccolum, various Compositae 

 {^Ambrosia, Chrysanthemum, Helianthus, Lactcea), Magnolia and 



