466 BOTANICAL GAZETTE [yUNE 
apparently indicated degeneration, were observed. In the zygospores he finds 
that multiple fusion with degeneration of the supernumerary nuclei takes 
place. The fusion is preceded by a division. Zygorynchus offers a variation 
from other forms in the fewness of the nuclei which fuse (4 in one species) and 
in the tardiness of the fusion. 
he process of zygospore formation in Zygorynchus, according to GRUBER," 
shows some peculiarities which have not been observed in mucors heretofore. 
The zygospore arises at the point of contact between the terminal portion of an 
erect hypha and a lateral branch arising from the same hypha or rarely from a 
different hypha. At the point of contact the gametangia grow out from each 
hypha, Only the female gametangium is cut off by a wall at its base from the 
parent cell. Later a partly formed wall arises midway between the base and 
apex in the female gametangium, but this wall is rarely completed and soon 
disappears. The male gametangium remains in connection with the parent 
hypha. After the fusion of the gametangium a differentiated portion of the 
protoplasm of the male gametangium passes into the female gametangium, 
ca g with it 20-30 nuclei. The fusion of nuclei was not observed on 
account of their minuteness. The author believes that a multiple fusion takes 
place and that subsequently the fused nuclei divide to give the large number 
subsequently found in the zygote. He does not note the reduction in number 
observed by Moreau. The resemblance of the manner of formation of the 
zygospore in this form to that of oospores suggests that Zygorynchus, which in 
other characteristics corresponds with the mucors, is akin to the oomycetes.— 
H. HASSELBRING. 
Cecidology.—A very interesting and valuable contribution is a study 
of a citrus tree cecidium caused by Sphaeropsis tumefaciens Hedges by HEDGES 
and Trenny.4 The organism was first isolated from lime tree knots from 
Jamaica in 1904. The knots vary in size from } to 3 inches, and are usually 
more or less spherical; they are light in color and smooth when young but 
become black and furrowed with age. The interior of the knot is hard and 
compact, while the outer part is soft and crumbling in character. They are 
frequently more or less covered with typical witches-broom growths. They 
occur on both old and young growths and at any season of the year, and eventu- 
ally cause the death of the plant. The mycelium may grow in any tissue, but 
is confined to the intercellular spaces, but unfortunately the authors have not 
given a discussion of the structural characters of the malformations. The 
fungus penetrates the wood for considerable distances beyond the point of 
inoculation, thus making pruning an unsatisfactory treatment. Pycnidia 
13 GRUBER, E., Einige Beobachtungen iiber den Befruchtungsvergang bei Zygoryn- 
chus Moelleri Vuill. Ber. Deutsch. Bot. Gesells. 30:126-133. pl. 1. 1912 
14 HEDGES, FLORENCE, and Tenny, L. S., A knot of citrus trees caused by Sphae- 
ropsis tumefaciens. Bull. no. 247. U.S. Dept. Agric. Bur. Pl. Industry. 1912. 
