No. 1, July, 1920] GENETICS ' L05 



shoots which produce intermittently green and variegated lea I variegated leaves 



arc pale green with white margins and have relatively large green sectors. (4) Samtmcua 

 nigra type, white margined Leaves that have a deep green central Geld and a pal*: green zone 

 of varying width between the central field and margin. The author states thai pun: albino 

 shoots do nol exist. Sooner or later such Bhoots produce leaves which have very small areas 

 of green, especially beneath thelower epidermis. Variegated leaves thai have the arras 

 ment of the colored and colorless areas in the above types inversed are referred to as inverse 

 variegation. Author points out thai Baur's explanation cannot account for isolated green 

 areas in the margin of leaves having the Saxifraga sarmentosa type of variegation, and that 

 it cannot at all explain the Spiraea Immalda type. He suggests that the phenomena of varie- 

 gation can be most simply explained by assuming reversible somatic mutation-, miewhat 

 analogous to Beyerinck's variegated race of bacteria, Chlorella variegata. It was observed 

 (1) that the frequency of mutation and subsequent development of variegation differs in the 

 various families and genera of plants, (2) that the frequency of mutation of cells at the growing 

 point differs at different stages of the shoot's growth, (3) that cells in different parts of the 

 same leaf blade do not mutate with the same frequency, and (4) that when variegated shoots 

 are cut back variegation is much more pronounced in the regenerated shoots. — W. II. Eyster. 



645. Laughlin, H. H. The relation between the number of chromosomes of a species and 

 the rate of elimination of mongrel blood by the pure-sire method. Proc. Soc. Biol, and Med. 

 16: 132-134. 1919. — The degree of elimination of mongrel "blood" by the pure-sire method 

 depends upon (a) the number of chromosomes characteristic of the species, (b) the proportion 

 of mixed dams of each possible pure chromosome-number used in each generation, (c) the 

 relative fecundity of dams of different pure chromosome-number, and (d) the number of 

 generations through which the system is carried. The probabilities of mongrel blood being 

 entirely eliminated in any given individual in generations one to ten in such a system, with 

 the calculations based on certain assumptions, are stated. — C. B. Hutchison. 



646. Lebius, Franz. Familienforschung. [Genealogical investigation.] 34 p. H. A. L. 

 Degener: Leipzig. 1918. 



647. Lehmann, Ernst. Die Pentasepalie in der Gattung Veronica und die Vererbungs- 

 weise der Pentasepalen Zwischenrassen. [Pentasepaly in the genus Veronica, and the man- 

 ner of inheritance of the eversporting varieties of the penta-sepalous forms.] Ber. Deutsch. 

 Bot. Ges. 36:28-46. Fig. 2. 1919. — In crossing the penta- and tetra-sepalous Veronica 

 Corrensiana with the penta-sepalous V. tubingensis we get in the Fi generation between 71 

 and 98 per cent penta-sepalous flowers. If we cross the tetra-sepalous V. Aschersoniana 

 with the penta-sepalous V. tubingensis we get in the Fi generation between 3 and 23 per 

 cent penta-sepalous flowers, that is, a dominance of the tetra-sepalous form, pentasepaly in 

 the first case being dominant, in the second case recessive. In the F 2 generation we get a large 

 percentage of tetra-sepalous flowers. By crossing them, a nearly pure pentasepalous form 

 with a nearly pure tetra-sepalous one, we get intermediate races — eversporting varieties — the 

 condition becoming more complex because of the change in dominance. In the Scrophu- 

 lariaceae, there are many members which show inhibition in the development on the dorsal 

 side of the flower primordium with a corresponding increase in growth on the proximal side. 

 This inhibition in growth may lead to a complete reduction of the distal median calyx lobe. 

 In the genus Veronica, this latter condition is nearly reached. Some forms show only a slight 

 reduction and in that case we do not get change from penta- to tetra-sepaly upon crossing; 

 that is, intermediate races do not appear. Other forms, such as V. tubingensis and some 

 Teutricum races, are intermediate. Another extreme is found in V. Corrensiana and V. 

 Aschersoniana, where penta-sepaly occurs only occasionally. Both extemes of phylogenetic 

 development may be connected by crossing; but the condition becomes complex because of 

 the appearance of intermediate races with a fluctuation in dominance of penta-sepaly and 

 tetra-sepaly. — Ernst Artschwagcr. 



