RECENT ADVANCES IN SCIENCE 389 



possesses evident air-chambers, but less numerous papillae 

 than D. velutina. Its most striking feature is, however, the 

 mode of occurrence of the male and female receptacles which 

 are found on the same plant, and of which five or six are 

 developed in succession on a series of terminal adventitious 

 shoots. Wiesnerella denudata is regarded as intermediate in 

 character between Dumortiera and Marchantia. 



Cytology and Genetics. — C. H. Farr (Am. Jour. Bot. July 

 191 8) describes the division of pollen mother-cells in Magnolia 

 tripetala. The cell-wall, it appears, is formed not by equatorial 

 thickening of the spindle-fibres, but by a constricting furrow 

 in which the cell-wall substance would seem to be deposited. 

 The significance of the chondriome forms the subject of a 

 paper by M. Guilliermond in the Revue generate de Botanique 

 for June. 



The Journal of Genetics for June contains a paper by Miss 

 Saunders dealing with two forms of the common foxglove. 

 Of these the common type exhibits a hairy stem (v. pubescens), 

 but there is also a smooth-stemmed variety which the author 

 terms nudicaulis. Both the varieties breed true to their 

 respective characters, the smooth behaving as a dominant and 

 the pubescent as a recessive. 



The mutations of (Enothera suaveolens are described by 

 De Fries (Genetics, 191 8). Six of these have occurred in the 

 cultures, three of which are represented by parallel mutations 

 in other species. Of the remainder two were narrow-leaved 

 types, whilst the third was frequently apetalous, though 

 exhibiting all conditions up to that with a perfect corolla. 



In the same journal Tupper and Bartlett deal with the 

 relation of mutational characters to cell size a propos of the 

 fact that the cells of a giant mutant of (Enothera pratincola 

 were found to be larger than those of the parent. The per- 

 tinent observations are reviewed. A doubling in the number 

 of chromosomes, accompanied by a marked increase in the 

 size of the cells, has been observed in Amblystegium serpens 

 bivalens and other mosses belonging to the genera Mnium and 

 Bryum ; in (Enothera mutants, of the species (E. Lamarckiana 

 and (E. stenomeres ; and in one of the " graft hybrids " of 

 Solanum ly coper sicum and Solanum nigrum. On the other 

 hand, the tetraploid variety of Phascum cuspidatum was a dwarf 

 with cells of the normal size, and the giant-celled mutants of 



