PUCCINIA GRAMINIS 



503 



into the spore, so that, in the course of a few minutes, the cell be- 

 comes practically empty and the spore laden with protoplasm. 

 The four septa doubtless 

 strengthen the basidium 

 mechanically, but I suspect 

 that they have another and 

 a more important physio- 

 logical function : possibly 

 by dividing up the long 

 tubular end of the basidium 

 into four equal cells they 

 make it simpler for the 

 protoplasm to be evenly 

 distributed among the 

 spores. 1 The appearance 

 of a teleutospore with two 

 fully developed basidia, one 

 bearing four full-grown 

 spores and the other with 

 its spores in course of dis- 

 charge, is shown in Fig. 

 204 at A.2 



The development of the 

 basidia and the formation 

 of spores takes place a few 

 hours after the teleutospores 

 have been moistened. The 

 rate of development of a 

 spore on the end of its 

 sterigma was carefully 

 observed several times. 

 Growth of a spore from its 



Cf. what was said concerning the septation of the basidia of the Auricularieae 

 in vol. ii, 1922, pp. 165-166. 



Fig. 204 is semi-diagrammatic. Living basidia of P. graminis are often much 

 more sharply curved than those there represented. The significance of basidial 

 curvature, which was not fully realised when Fig. 204 was drawn, is treated of in 

 the next Chapter. 



Fig. 203. — Puccinia graminis. a to g, normal 

 development of a basidiospore and its dis- 

 charge from the sterigma. a, the sterigma ; 

 b, the first rudiment of the spore, a hilum 

 has been developed ; c, the spore in a 

 lateral position, half -grown ; d, the spore 

 full-grown. Stage d is about 20 minutes 

 after stage a. Between d and e there is a 

 pause of the order of an hour, e, a drop 

 of water is beginning to appear at the hilum ; 

 /, five seconds later, the drop has attained 

 its maximum size. The spore is then 

 immediately shot away as shown at g. h to 

 I, abnormal germination of undischarged 

 spores on the ends of their sterigmata. The 

 sterigmata have grown into the air from 

 submerged basidia. h, a spore with an 

 unbranclied germ-tube ; i, a spore with a 

 branched germ-tube. The spore shown at 

 j germinated, as shown at k. Its germ- 

 tube produced another spore which germi- 

 nated, /. Magnification, 880. 



