MODELS OF BASIDIA 519 



graminis and Endophyllum Euphorbiae-sylvaticae. This pheno- 

 menon was demonstrated to a research-worker, Mr. W. F. Hanna, 

 as follows. I observed a basidiospore intently and, as soon as a 

 drop began to appear on the spore-hilum, I asked Mr. Hanna to 

 look down the microscope. He did so and, in the course of about 

 10 seconds, saw the drop grow to full size and then the drop and 

 spore violently discharged from the sterigma. 



Each basidiospore is set obliquely on the end of its sterigma 

 from the first, as in Puccinia graminis and the Uredineae in general. 

 During the excretion of the drop, a basidiospore does not become 

 pushed to one side, as believed by Weimar,^ but remains unmoved. 



Finally, it may be mentioned that the discharge of the basidio- 

 spores from Cedar galls can be very well seen, and demonstrated 

 to students, by means of the beam-of-light method described in 

 Volume 1.2 When an active gall is suspended at the top of a 

 covered beaker and a beam of light is directed through the air just 

 below the gelatinous horns, the individual basidiospores, as they are 

 shot away from the horns and spring into the light, can be perceived 

 quite readily as white particles falling by their own weight or being 

 carried hither and thither by convection currents in the air. 



Models of Basidia. — For use with audiences of students and 

 others, I have had constructed two large models representing 

 respectively the curved basidium of a Rust fungus {Puccinia 

 Malvacearum) and the straight basidium of a Hymenomycete 

 (generalised). These models are photographically reproduced in 

 Fig. 212. The taller of the two is two feet high. In the Rust 

 model (to the left) one sees a two-celled teleutospore bearing a 

 curved basidium-body with four sterigmata and four spores. The 

 model is detachable from its stand, the basidium detachable from 

 the upper cell of the teleutospore, and the four spores detachable 

 from their sterigmata. In the hymenomycetous model (to the 

 right) one sees a straight basidium-body bearing four sterigmata 

 and four spores. Again the model is detachable from its stand and 



^ J. L. Weimar, " Three Cedar Rust Fungi. Their Life-histories and the 

 Diseases they Produce," Cornell University Agricultural Experiment Station, 

 Bull. 390, 1917, pp. 523-524. 



2 These Researches, vol. i, 1909, pp. 94-101. 



