200 SCIENCE PROGRESS 



problems in the genus Rosa {Trans. Nat. Hist. Soc. Northumber- 

 land, Durham, and Newcastle) Heslop Harrison shows that the 

 northern roses fall into eight series or "section-species," in 

 each of which parallel forms are recognised, and which the 

 author regards as examples of orthogenesis. Examination 

 of the pollen showed that this was usually largely, or in part, 

 abortive, indicating widespread hybridity. Several forms, 

 especially those with high chromosome numbers, exhibit 

 apogamy, and polyembryony occurs. 



The same author and Miss Blackburn {Ann. Bot., April) 

 consider the cytological details, from which it appears that the 

 normal haploid chromosome number in Rosa is seven. Failure 

 of reduction, however, would appear to be frequent. Rosa 

 arvensis and R. rugosa were found to be diploid ; all the 

 Eucaninse, Afzelianae, Rubiginosae, Tomentosae, and one hybrid 

 were pentaploid, whilst R. pimpinellifolia X R. tomentosa v. 

 sylvestris was found to be hexaploid. 



Ecology. — Seeds of Douglas Fir from a variety of localities 

 have been raised by Hoffman {Ecology, April). He finds a 

 decrease in the percentage germination of the seeds and 

 diminished vigour in the seedlings with increasing age of the 

 parent tree or with increasing altitude of its situation. An 

 unhealthy condition of the parents also has the same effect 

 on the seeds and seedlings raised from them. 



Somewhat diverse results have been obtained relative to 

 dormancy in the Cocklebur {Xanthium). McHargue has 

 reinvestigated the question and finds that the larger seed in 

 the two-seeded burr normally germinates first and is the 

 more vigorous, whilst the germination of the smaller may be 

 delayed till the succeeding season. When removed from the 

 burrs, however, there was no apparent difference in behaviour 

 between the two. 



Taxonomy. — Several papers of interest to British botanists 

 have appeared in recent numbers of the Journal of Botany ; 

 these include : Forms of Orchis macitlata (May), by T. and T. A. 

 Stevenson ; forms of Matricaria inodora, by Lester-Garland ; 

 Potamogetons of the English lakes, by W. H. Pearsall (June) ; 

 and new British Sphagna and Hepatics are described by J. A. 

 Wheldon and W. E. Nicholson (July). A useful key to the 

 Harpidioid Hypna is being contributed to the Naturalist by 

 J. A. Wheldon. 



The North American species of Piper belonging to the 

 section Ottonia are the subject of a paper by Trelease in the 

 Anier. Journ. Bot. for April. Eight new species are described, 

 and their variability with respect to what are usually re- 

 garded as important characters is a striking feature. Thus, 

 whilst in most species the gynoecium consists of 3 carpels in 



