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THE AMEBIC AN NATURALIST [Vol. XLIV 



to each other and to the original sexual reproduction of 

 the group much clearer. In the smuts we have an endo- 

 karyogamy in the smut spore. In Entyloma the myce- 

 lium from which the spore arises is binucleated at least 

 in the later stages of its development. In Ustilago the 

 mycelial cells are multinucleated and there is less evi- 

 dence for the separate ancestry of the nuclei in the smut 

 spore. 



The conjugations of the conidia regarded by DeBary 

 as sexual unions represent the only normal conjugation 

 of gametes in the life cycle, but they are plainly only of 

 sporadic occurrence. Certainly they are not necessary to 

 the completion of the normal development of the smut 

 and they may probably be assumed to be in process of 

 disappearance. The behavior of the nuclei in these 

 fusing conidia favors this view. Federley finds them 

 fusing in normal fashion in the smut of salsify. Lutman 

 finds also that the nuclei may fuse in the conjugation of 

 the promycelial cells of the oat smut. Dangeard finds 

 they do not fuse in the conidia of Tilletia and according 

 to my own observation the same is true in the conjugation 

 of the conidia of the anther smut, though here many of 

 the ordinary effects of sexual fusion appear in the con- 

 jugated pairs of conidia. 



Lutman shows that infection and the normal develop- 

 ment of oat smut may occur without any such fusions, 

 and that hence the later nuclear fusion in the smut spore 

 can not possibly be a delayed fusion of nuclei which came 

 together in an earlier normal cell fusion of gametes. 

 The endokaryogamy in the smut spore appears here as a 

 distinct process which has originated independently of 

 the normal sexual fusion, though it may have secondarily 

 developed sexual significance with the development of 

 conjugate division in the mycelial cells from which the 

 smut spores arise, and have thus made possible the en- 

 tire disappearance of the original normal sexual repro- 

 duction. 



From this standpoint we are justified still further in 



