1919] CURRENT LITERATURE 95 



the internal structure of the seeds, especially the smaller seeds, might help to 

 connect the Cordaitales with the Pteridophytes. 



The fact that the geographical distribution of plants at different stages in 

 the development of the earth receives only disconnected treatment is excused 

 by the plea that the space needed for Vols. Ill and IV (now in press) was 

 underestimated, the original plan providing for a treatment of geographical 

 distribution at the end of Vol. IV. How^ever, Seward promises an entire volume 

 devoted to this subject. Such a work would be welcomed by all students of 

 morphology and phylogeny, and we hope that the volume will make its appear- 

 ance at an early date. 



The complete bibliography and index, together with the critical and con- 

 servative presentation of the entire subject, make the work indispensable to 

 those engaged in research upon fossil plants.— C. J. Chamberlain. 



NOTES FOR STUDENTS 



Chlorophyll inheritance.— This subject seems to be a stumbhng-block 

 both for plant geneticists and cytologists. In 1913 Emerson and East^ 

 stated that there were on record only two indisputable cases of non-Mendelian 

 inheritance. Both of these were cases of chlorophyll inheritance. Correns* 

 made reciprocal crosses of a variegated Mirabilis {albomacidata) with normal 

 green plants, and discovered that in this case inheritance was strictly maternal^ 

 the pollen evidently contributing nothing. He explained this by assuming 

 that the variegation was due to a disease of the cytoplasm which destroyed 

 many of the chloroplasts, and that nuclei were immune to this disease. Thus 

 the disease could be transmitted to progeny by the female parent only, since 

 the male is supposed by cytologists to contribute only a nucleus stripped free 

 from its cytoplasm. If one grants Correns' assumptions, the mechanism 

 provided will explain this case of maternal inheritance without any violation 

 of Mendel's law, for here there would be no true inheritance, but merely 

 reinfection. 



Baur,'< working with a Pelargonium which had white-margined leaves, 

 observed an occasional pure green branch and an occasional pure white branch. 

 Flowers on these branches when self-fertilized gave respectively pure green 

 and pure white progeny (the latter, of course, dying in the seedling stage). 

 A cross either way between the two branches resulted in progeny which were 

 a mosaic of green and white. Such behavior can be accounted for by either 

 of two explanations, but each involves a very bold assumption. If there is a 

 MendeHan determiner responsible for the full green development, and a white 



' Emerson, R. A., and East, E. M., Inheritance of quantitative characters in 

 maize. Bull. Agric. Exper. Sta. Nebr. no. 2. pp. 120. figs. 21. 1913. 

 3 Correns, C. E., Zeitschr. Ind. Abstamm. Vererb. 2:331-340. 1909. 

 ■• Baur, Erwin, Zeitschr. Ind. Abstamm. Vererb. 1:330. 1909. 



