s,) PHYLOGENY 



spenno^.iH's. The Hr>t sta^i- <»f evolution was the separation 

 of this spore-form into two, one (the secidiospore) germinating 

 conidially, the other (the teleutospore) following it and germi- 

 nating basidially : types approximating to this stage are seen 

 in the section Pucciniopsis. It is quite certain that uredospores 

 are only modified aecidiospores, formed as a mere multiplying 

 device without the intervention of another fusion-cell. The 

 peridium which is found in these later stages of evolution round 

 the aecidium was at first represented (doubtless even in the 

 primitive Endophyllum) by a mere circle of paraphyses or 

 not at all. 



From a cytological point of view, the fusion of the two 

 nuclei in the teleutospore may be taken as paralleled by the 

 similar fusion in the basidium of the Basidiomycetes; the 

 division into four basidiospores follows in both cases, although 

 the mechanism is different. If the view propounded in a 

 previous chapter is adopted, that the four cells of the "basidium" 

 of the Uredinales are the real tetraspores 1 and the basidiospores 

 are merely conidia whose function is to facilitate dispersion by 

 wind, it will be seen that the difference in the Basidiomycetes 

 consists in the fact that cell-walls are not formed round the 

 tetraspores previously to the production of conidia. This may 

 recall the fact that in the Red Algae the four spores in a tetra- 

 sporangium are also not surrounded by cell-walls before their 

 discharge into the water. Of course, in the subaerial Uredinales 

 and Basidiomycetes such naked masses of protoplasm would be 

 comparatively ineffective for propagation, and are here replaced 

 by methods more suitable to a land environment. The throw- 

 ing off of the basidiospores with a jerk appears to be the same 

 in both these groups. 



A similar comparison with the Ascomycetes cannot be made 

 with equal advantage, until the students of that group of Fungi 

 have come to some semblance of agreement as to the actual 

 course of its cytological history. But it is impossible to over- 

 look the remarkable parallelism between the cytology of the 



1 In the Himalayan Barclayella, which is placed among the Melampsor- 

 aceae ("?), these tetraspores are said to round themselves off and separate, 

 apparently as the normal mode, without forming basidiospores. 



