258 v BOTANICAL GAZETTE [September 



In an appendix the author shows that the increase in proportion of doubles 

 derivable from old seed is due to the greater longevity of the seeds which lack 

 X and Y, and not to any change in the genotypic nature of any single seed. 

 She also tried to separate singles and doubles on the basis of seed-characters, 

 but was able to do this only in the sulfur-white race, and then not by the 

 character for doubleness, but by the white or cream plastid-color, which as 

 stated above proved to be coupled with one of the factors for singleness. Ten- 

 week stocks are much branched and the Brompton stocks unbranched. The 

 unbranched condition is recessive, but the ratio is somewhat modified because 

 typically unbranched plants will develop some branches when the terminal 

 bud is injured. Notes are also appended regarding the inheritance of several 

 sap-colors, rose, lilac, terra-cotta, carmine, and crimson. — Geo. H. Shull. 



Biology and taxonomy of Gymnosporangium. — A monograph treat- 

 ing of Gymnosporangium both in its biological and its taxonomic aspects is 

 the outcome of several years of experimental and observational work on that 

 genus by Kern. 12 The work is divided into two parts, the first dealing with 

 the biology and the second with the taxonomy of the genus. 



In Part I the biology of the genus is discussed under the following general 

 heads: Introduction (including the life history, general characteristics, and 

 nuclear phenomena), distribution and relationships, experimental investi- 

 gations of life histories, and pathological and economic importance. Particu- 

 lar attention is given to the geographical distribution of the species with 

 reference to the distribution of their hosts. The main facts are arranged in 

 convenient tables. The forms associated with the two sections of Juniperus 

 present the most interesting features in regard to their distribution. The 

 species which occur on the section Sabina belong either exclusively to the 

 western or exclusively to the eastern hemisphere, while of those occurring 

 on species of the section Oxycedrus some are common to both hemispheres 

 and others are limited to one hemisphere. These facts lead the author to 

 the conclusion that the forms found on the older section {Oxycedrus), some of 

 whose species are distributed over all the continents of the northern hemisphere, 

 were distributed with their hosts "during a geological period when the land 

 conditions permitted migrations between the northern continents." The 

 author supposes that the section Sabina has developed from the section Oxy- 

 cedrus since the continents have become isolated, therefore "we would not 

 expect to find the same species, either of hosts or fungi, indigenous in North 

 America and in the Old World; and this, indeed, is the case-" This view of 

 course implies the independent origin of species of the section Sabina in the 

 two hemispheres. 



Regarding the limited geographical distribution of species of Gymno- 

 sporangium in cases where both the hosts have a wider distribution, no satis- 



13 Kern, Frank Dunn, A biologic and taxonomic study of the genus Gymnospo- 

 rangium. Bull, N.Y. Bot. Gard. 7:392-494. 191 1. 



