yEcidiospores. 23 



spores of Chrysomyxd) the alternate cells remain sterile, 

 so that instead of a long continuous series of spores, we 

 encounter a series of perfect spores alternating, with 

 variously shaped abortive cells, which may be shrivelled into 

 fibres as in Rcestelia (Plate II. Fig. 9), or variously flattened as 

 in CJirysomyxa (Plate II. Fig. 8). The further development 

 of the spores consists in the cuticularization of their exterior. 

 How this cuticle arises is not clear, whether from a meta- 

 morphosis of the mother-cell, or from a separate develop- 

 ment. The cuticle is in almost all species variously 

 roughened by a number of minute points, spines, or very 

 minute warty protuberances. By treatment with caustic 

 potash these prominences disappear. According to De 

 Bary's* most recent views, he would appear to maintain 

 that all gecidiospores are developed with alternate abortive 

 cells. 



The pseudoperidium of the secidia is formed in the 

 same manner as the spore-series, only the cells are sterile 

 and empty, instead of being filled with coloured proto- 

 plasm (endochrome). They are, however, developed in 

 linear series, the larger and more mature being uppermost, 

 the younger and smaller below; in fact, we may look upon 

 the peridium as being developed from a circle of basidia 

 surrounding the hymenium. The pseudoperidial cells are 

 held pretty firmly together by an intercellular substance. 

 They are variously altered by mutual pressure, being 

 flattened, oval, oblong, square or rhomboidal, and always 

 larger than the spores. The peridial cell-series are con- 

 tinued upwards until they arch over the spores and meet 

 those of the opposite side, so that they form a complete 

 investment above and around the ascidium. As this body 

 grows it comes nearer the surface, until at last it is covered 

 by the epidermis alone, through which it may be seen 



* De Bar)', " Vergleichende Morphologic und Biologic der Pilze," p. 76. 



