28 TK'I'i: VSPORE-MOTHER-CELL 



The beleuto3pore-cell is a sporo-mother-cell, exactly com- 

 parable with a tetraspore-mol her-cell. The" basidium" is merely 

 tlif same cell, removed outside the old outer cell-wall for the 

 convenience of the ensuing processes; in Goleosporium this 

 removal does ool lake place, bul the "basidium" is formed 

 internally, the mucilaginous nature of the cell-walls of the 

 teleutospores of thai genus allowing the sterigmata to protrude 

 through them (see Fig. 241 >, which could qo1 be done through 

 the hard cutinised cell-walls of the teleutospores of Puccini" 

 ( \i ricis. 



The Hist division of the nucleus of the beleutospore is 

 heterotypic, and really initiates the gametophyte; but, since 

 this is not a sufficiently definite point in the cycle, it is usual 

 to consider the gametophyte to begin after the next division, 

 i.e. by the formation of the four basidium cells, which constitute 

 a tetrad. These four cells are the true tetraspores. In water, 

 deprived of air, they can each send out a germ-tube and, it is 

 presumable, could cause infection. The formation of basidio- 

 spores on sterigmata is a secondary process, viz. the product ion 

 of conidia suitable for wind-dispersion: this is shown by the 

 fact that, if the basidiospores are not on the proper host plant, 

 they can themselves germinate with the production of fresh 

 conidia of an exactly similar character. 



The mycelium (thallus) of the gametophyte, issuing from 

 the basidiospores, bears male and female organs, the spermo- 

 gones and aecidia. The spermatia disintegrate without any 

 result: the "fertile" cells of the secidium (usually, perhaps 

 nearly always, after cutting off a sterile cell, as is the habit of 

 female gametes) are stimulated to further growth by con- 

 jugation with one another, the delay in the fusion of the nuclei 

 being of little or no importance from this point of view. This 

 so-formed fusion-cell is a zygote and is the beginning of the 

 sporophyte. The recidiospores and uredospores which are borne 

 by this are conidial forms, devoted to increased multiplication, 

 and may continue indefinitely till the time arises for beginning 

 the cycle again. This is indicated by the dotted lines on the 

 left of the diagram. 



It is known that a fusion of two nuclei, comparable with that 



