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1907] CURRENT LITERATURE 



75 



tales originated, the first group retaining the characters of the primitive type;" 

 and that the Lycopodialcs "may perhaps be regarded as an extreme case of leaf 

 reduction in one of these lines." — J. M. C. 



Apogamy in Hieracium. — Rosenberg=*3 finds that in Hieracium auricula 

 and H, venosum the development of pollen and embryo sacs is normal and fertili- 

 zation occurs regularly; there are 9 chromosomes in the gametophyte, 18 in the 

 sporophyte, and 27 in the endosperm. Most species of Hieracium, however, are 

 apogamous, and their embryo sacs are formed without any reduction division. 

 Usually they do not arise from megaspores, but from cells of the integument or 

 chalaza; that is, the gametophyte is aposporous and crintains the sporophytic num- 

 ber of chromosomes. In H. excellens an embryo sac with the reduced number 

 of chromosomes is often formed, but there are usually aposporous sacs in the 

 same head. This shows why //. excellens, in spite of its being apogamous, may 



J. also produce hybrids. — Charles J. Chamberlain, 



Geographic distribution of closely related specijBs. — Lea\7TT''* has published 



a study of the distribution of species in reference to their evolution. The topics 



i discussed are " the effects of different evolutionary agencies upon specific distribu- 



tion, *the necessity of isolation and Mendelian inheritance," "specific distribu- 



tion in the animal kingdom," '*the distribution of plants," and "evidence from 



' North American Orchidaceae." The problems are stated and solutions are not 



attempted, but the impression of the author is that a study of the specific distribu- 

 tion of plants is not likely to be unfavorable to mutation as one method of evolu- 

 tion. He thinks that "the adherents of mutation will be able to bring forward 



enough cases of social distribution to render phytogeographic weapons useless in 

 the attack upon this theory." — J. M. C. 



, Cytology of apospory, — Nephrodinm pseudo-mas Rich. var. cristaia apospora 



apospory 



^ be found. 



apogamy except parthenogenesis. Several fronds pegged down quickly produced 

 prothallia at the tips of the leaves, and these prothallia within three wrecks bear 

 pogamous embrvos. Antheridia are not uncommon, but no archegonia could 



aposjx)rous 



thalli 



apogamous 



chromosomes. In N. pseudo-mas Rich. var. polydaclyla Wills, migrating nuclei, 



be 



var. cristata apospora Druer>' there seems to be no migration or fusion of nuclei. 



Charles T. Chamberlain. 



*3 Rosenberg, O., Cytological studies on the apogamy in Hieracium. Bot. Tids- 

 skrift 28:143-170. pis, 1-2. 1907. 

 I ^'^ Leavitt, Robert Greenleaf, The geographic distribution of closely related 



species. Amer. Nat. 41:207-240. 1907. 



5 DiGBY, L., On the cytology of apogamy and apospory. II. Preliminary note on 



apospory. Proc. Roy. Soc. Lo 



