1907] CURRENT LITERATURE 75 
“Droppers”’ of Tulipa and Erythronium.—Miss RoBERTSON'S has been 
investigating the peculiar descending stolons of Tulipa and Erythronium, which 
are called ‘‘droppers”’ by the gardeners. In her account she makes no mention 
of the work of Rrmpacu,'® one of whose papers contains quite an extended 
account of the “droppers” of Erythronium, and the other deals with a number 
of genera of the Liliaceae. The summary states that “the power of lateral 
migration to prevent overcrowding, and of descent into the soil for protection 
against frost, drought, and animals, is possessed in some degree by many bulbous 
plants.”’ The statement includes a fact and its purpose; the former seems evident, 
the latter would be somewhat difficult to demonstrate. The power referred to is 
said to be more highly specialized in Tulipa and Erythronium than usual, and 
hence the structure and behavior of the so-called ‘‘droppers”’ is of special interest 
“The immature bulb each year produces a single foliage leaf, continued at the 
base into a hollow tube, the ‘dropper,’ enclosing a bulb at its tip.” It seems to be 
a distinct device for distributing bulbs; and the testimony of anatomy is that the 
“dropper” is partly axial and partly foliar.—J. M. C 
Laws of heredity classified —DaRBISHIRE'? draws a careful distinction 
between the several so-called laws of inheritance now under discussion among 
biologists. He classifies them as statistical and physiological according as they 
are descriptive and deal with mass-results on the one hand, or as they are explan- 
atory and deal with individuals on the other. He places GALTON’s and PEAR- 
SON’S laws in the former category, and Mendelism and the law of diminishing 
contribution in the latter. By the law of diminishing contribution he designates 
the view generally held that an individual inherits more or less from all his ances- 
tors, but less from the more remote than from the more recent. It is main- 
tained that Mendelism is not to be considered alone as a theory, but also as a 
method, and that new details of theory which are worked out by the Mendelian 
method are as much a part of Mendelism as is the original statement made by 
MENDEL. An experiment is outlined which is calculated to test simultaneously 
the truth both of Gatron’s and of MENDEL’S laws, and it is pointed out that 
the former is true of masses and the latter of individuals—Gro. H. SHULL. 
Radial growth of tree-trunks.—LiGNrER" has been investigating the growth 
of trees in diameter, following a suggestion made A. De CANDOLLE in his Physi- 
ologie végétale ( 1832) that if there could be made a very large number of obser- 
vations of individuals of the same species, an approximate formula of increase 
tS ROBERTSON, AGNES, The Beal of Tulipa and Erythronium. Annals of 
Botany 20: 429-440, pls. 31-32. 1906. 
6 Bor. GAZETTE 30:171-188. pl. 13. 1900; 332401-420. pl. 14. 1902. 
7 Darsisuire. A. D., On the difference between physiological and statistical 
laws of heredity. ai and Proc. Manchester Lit. Phil. Soc. 50 (no. 11): 44. 1906. 
8 LicNIER, O., Notes sur ]’accroissement radial des troncs. Bull. Soc. Linn. 
Normandie V. 9:181-224. 1905. 
