1913] CURRENT LITERATURE 407 
He does indeed give two plates of frequency polygons, but his distributions 
are for number of flowers measured on particular dates, with no statement 
as to their size, and for relative frequency of flowers of certain sizes, with no 
data on the actual number of flowers measured or the number of plants upon 
which they were borne. Apparently the parents upon which data were taken 
were too few to warrant such sweeping conclusions. 
In the second paper, also, one gathers that the F, generation there reported 
on is more variable than the F, generation; but no data are recorded. This 
paper purports only to be a note, however, and one may expect some data of 
greater consequence when the really sid amount of work that the writer has 
done is reported in full—E. M. Eas 
Knot disease of citrus trees.—Herpcrs and TENNY? give a complete 
account of a knot disease of citrus trees that had been briefly described in a 
preliminary account by Miss Hepces.” The disease has been found on lime 
trees in Jamaica and in one instance in Florida. It manifests itself by woody 
knots or swellings which appear on the branches and trunks of the diseased 
trees. The knots are usually round or somewhat elongated in the direction of 
the axis of the branch which bears them. They attain a diameter of 2-3 
inches, and by their growth usually girdle the branch upon which they are 
seated, this causing the death of all the parts of the branch above the knot. 
Groups of fascicled branches, forming witches-brooms, often grow out from the 
knots, but these branches also are short-lived. The knots consist mostly of 
woody tissue, at first covered by bark which soon dies and crumbles away. All 
the tissues of the knots, as well as the tissues of the branches near the knots, 
are found to be infected with the brown mycelium of a fungus which was 
described by Miss Hepcrs as Sphaeropsis tumefaciens. The mycelium of 
this parasite has been observed to spread to a distance of 45 cm., and it seems 
probable that it can spread to greater distances. Secondary knots are pro- 
duced by the mycelium which spreads through the branches. The growth of 
the fungus on a large number of media, its characteristics, and numerous 
infection experiments are described at length by the authors.—H. HasseEt- 
BRING 
The cause of leaf asymmetry.—Bosnart, working in GOEBEL’s labora- 
tory, reports the results of certain observations and experiments on asymmetry 
and anisophylly.* He concludes that the size of any given leaf part is deter- 
mined by the area it occupies in the vegetative point. Further development 
9Hences, F., and Tenny, L. S., A knot of citrus trees caused by Sphaeropsis 
insuaficdaal Bur. Pl. Ind. Bull. 247. pp. 9-74. pls. 10. figs. 8. 1912. 
*” HEDGES, FLORENCE, Sphaeropsis rascetgy nov, sp., the cause of the lime and 
orange knot. pmo 1263-65. pl. I 
™ Boswart, K., Beitrige zur ack a Blattasymmetrie und Exotrophie. 
Flora sé teccee Igtt. 
