376 BOTANICAL GAZETTE ^ [april 



are very young but do not seem to have been well preserved. If material in 

 this stage and somewhat older stages could be secured, it would help immensely 

 in comparing the Bennettitales and the Cycadales. — C. J. Chamberlain. 



Cytology of the basidium. — A cytological investigation of the basidium of 

 Eocronartium muscicola, one of the Auriculariales parasitic upon mosses, was 

 undertaken by Fitzpatrick'^ because he had noticed that the nuclei are of 

 unusual size, and because very little cytological work has been done in this 

 order. The mycelium, which is intracellular and extends throughout the host, 

 is composed of binucleate cells. The cells of the sporophore are also binucleate, 

 and, during division, it is seen that the number of chromosomes in each of the 

 2 nuclei is 4. During the development of the basidium, the 2 nuclei fuse, the 

 resulting nucleus passes into synapsis, and in later stages of division shows 4 

 chromosomes, which is also the number at the second division, so that the total 

 number of chromosomes in the cell is reduced. Toward the close of the second 

 division a transverse wall appears in the middle of the basidium and is soon 

 followed by two more walls, so that the basidium consists of a filament of 4 

 cells. The sterigmata, which are large in proportion to the cells from which 

 they arise, are not quite simultaneous in their appearance. The chromatin 

 becomes drawn out into a slender thread as the nuclei pass into the young 

 spores, and there is no connection with the centrosomes, as has been reported 

 for some basidia. How the binucleate mycehum arises from the uninucleate 

 spore has not yet been determined. — ^C. J. Chamberlain. 



Orientation of roots. — Holman"! has investigated the influence of the 

 medium upon the orientation of primary terrestrial roots. He shows that the 

 failure of roots grown in air to reach a vertical position is due to lack of mechan- 

 ical resistance to the advance of the root tip after the flattening of the primary 

 geotropic curvature, rather than to differences in water content in the medium, 

 or changes in geotropic sensitiveness, or to thigmotropism. His observations 

 have been extended to secondary roots,'s and here also he finds that when they 

 have been displaced from normal position with respect to gravity, and the first 

 curvature of response has been flattened, mechanical resistance is necessary to 

 a complete reaction to normal position. The mechanical resistance hinders 

 flattening of the primary curvature of the root tip, and passively depresses the 

 tip as it moves forward, thus reinforcing and completing the geotropic response. 

 — C. A. Shull. 



'3 FiTZPATRiCK, H. M., The cytology of Eocronartium muscicola. Amer. Jour. 

 Bot. 5:397-419. ph. 30-32. 1918. 



"• HOLMAN, Richard M., The orientation of primary terrestrial roots with particu- 

 lar reference to the medium in which they are grown. Amer. Jour. Bot. 3:274-318. 

 1916. 



's , Influence of the medium upon the orientation of secondary terrestrial 



roots. Amer. Jour. Bot. 3:407-414. 1916. 



