Christman—Development of the Primary Uredospore. 523 
be reckoned with by those who assume that these are at present 
functionless. 
Further data must be had before these difficulties can be 
cleared up, and meanwhile it is clear that in their general char¬ 
acter the fusions found in the development of the aecidiospores 
of Phragmidium speciosum, Caeoma nitens, Uromyces caladii 
and Melampsora rostrupi , and in the development of the pri¬ 
mary uredospores of Phragmidium potentillae canadensis are 
strikingly similar to the unions of equal gametes as found in 
the lower fungi. I am inclined to believe also that the nuclear 
migrations described for a long series of forms studied by 
Blackman (1) and by Blackman and Fraser (2) are to be in¬ 
terpreted in the light of this resemblance. Distortions of the 
vegetative structure of the fungus might lead, as noted above, 
to the substitution of such nuclear migrations for the original 
cell fusions. 
Blackman has used the term “basal cell” to indicate that 
structure from which the aecidiospores arise, whether it be the 
product of the fusion of two equal cells or the result of a mi¬ 
gration fertilization. There are obvious objections to this 
usage which become more marked in such forms as Puccinia 
adoxae, where the nuclear migrations may be several cell gener¬ 
ations removed from the base of the aecidium pustule. I shall 
refer to the product of the fusion of the two equal gametes as 
the “fusion cell,” and use the term “basal cell” for the direct 
product of this fusion cell in its germination. 
It is, however, my chief purpose at this time to bring out 
the resemblance between the true aecidium and the primary 
uredo. That the spores in the two cases are in every way 
morphological equivalents cannot be doubted. Whatever the 
function of the intercalary cell may be, there can be no ques¬ 
tion that, as Sapp in.-Trouff y has pointed out, though misin¬ 
terpreting the fusion cell, it is the morphological equivalent 
of the stalk of the primary uredospore, even though it serves a 
different mechanical purpose in the latter case. The fact that 
the two bases of the fusion cell do not remain so distinct here 
as they do in Phragmidium speciosum is not of great moment. 
