ZOOLOGY AND BOTANY, MICROSCOPY, ETC.* 
71 
strains is vigorous and of rapid growth. Inbred plants develop more 
slowly than crossbred plants throughout the entire period of growth, 
and sometimes have sterile pollen. Vigour and' development are un- 
affected by improved conditions of growth. The present work confirms 
the results obtained by East and Jones with maize, and show that the 
immediate results of inbreeding naturally cross-fertilized species are 
injurious ; this appears to be true in all cases where similar conditions 
affect sexual reproduction. S. G. 
Interspecific Hybrids in Crepis. — E. B. Babcock and J. L. Collins 
{Tom. cit ., 194-204, 2 pis.) have studied hybrids of Crepis capillaris 
and C. tectorum with special reference to the chromosome theory of 
heredity. These species were selected as suitable for investigation 
because of the small number of their chromosomes, C. capillaris having 
three pairs and C. tectorum four pairs. It was found that reciprocal 
crosses were equivalent. The F 2 generation showed dominance of the 
tectorum characters of the cotyledon, and the greater vigour of growth, 
as exhibited in greater size of the parts of the seedling. No plant 
survived the cotyledon stage, owing to the absence of organization and 
co-ordination of the functioning systems. It has been suggested that 
species of a large number of chromosomes may have originated from 
species with a smaller number, owing to fragmentation or segmentation 
of the latter. The results of the present work show that C. tectorum 
cannot be related in this way to C. capillaris. S. G. 
Chemical Method of Distinguishing Genetic Types of Rudbeckia. 
— Albert F. Blakeslee (Zeitsch. Abstamm. u . Vererbungsl . Berlin , 
1921, 25, 211-21, 1 pi.). An account of an attempt to resolve 
phenotypes into genetic groups by means of chemical reagents. 
Observations have shown that while the cones of Rudbeckia hirta 
usually have purple cones, two genetic types have yellow cones. In 
appearance the two types are indistinguishable, but they are found to 
give different colour changes when the cones are treated with various 
chemicals. In one type, known as the Black Yellow, the cones turn 
black when treated with a caustic alkali, while in the other type, which 
is known as the Red Yellow, the cones turn red w 7 hen treated with these 
alkalis. Both the Black Yellow and the Red Yellow characters are 
inherited as simple Mendelian recessives. When crossed the F x genera- 
tion consists of purple-coned individuals. In the F 2 generation purples 
are to yellows in the ratio 9 : 7. The results show that genes for Black 
Yellow and Red Yellow are in different chromosomes. Further 
experiments in the same direction appear to be desirable S. G. 
CRYPTOGAMS. 
Pteridophyta. 
Structure in Palaeozoic Bituminous Coals. — Reinhardt Thiessen 
(. Department of the Interior, Bureau of Mines, Bulletin 117, Washington , 
Government Printing Office, 1920, 296 pp., 160 pis.). This richly 
illustrated report contains chapters on the work of previous investigators, 
