274 BOTANICAL GAZETTE [APRIL 
features of sexual conjugations as found in other plants and animals. 
Superficially considered, RAcIBoRSKI’s’ conception that the sexual 
union may be regarded as consisting of two phases, cell fusion and 
nuclear fusion, might seem to fit the conditions found in the rusts. 
I am inclined, however, to accept BLACKMAN’s conclusion that the 
fusion in the teleutospore has wholly to do with the reduction of the 
number of chromosomes. 
The difference between the method of conjugation in P. violaceum 
as described by BLACKMAN and P. speciosum as I have described it 
above indicates the necessity for a comparative study of a large 
number of aecidia to determine the nature of the sexual process in 
the group as a whole. There can be no question, however, that with 
the discoveries already made the existence of true sexual cell fusions 
in the rusts is finally established. , 
The writer feels greatly indebted to Professor ARTHUR for the 
careful selection and fixation of the material used in this work, and 
to Professor Harper for valuable suggestions and kindly assistance 
in many ways. 
THE UNIVERSITY OF WISCONSIN, 
Madison, Wis. 
EXPLANATION OF PLATE VIII. 
The figures were drawn with the camera lucida. Figs. 1, 2, 10, 17 » and : . 
were drawn using the Bausch & Lomb r-inch eyepiece and +(x oil objective; al 
others were drawn with }-inch eyepiece and jy objective, the tube length in either 
case being 185™™. 
Phragmidium speciosum. 
Fic. 1. Hyphae massing beneath the epidermis in the early stages of 1 
ma. ; 
Fic. 2. The series of large cells formed preparatory to division into wee 
cell and gamete; a and 4, cells lying close together, which appear to be parts 
different hyphal branches. oss: toe, Cee Te 
Fic. 3. A cell of such a series as is shown in fig. 2 after the division into 
smaller sterile cell and the large gamete. 
Fic. 4. Two gametes about to fuse; sterile cells remain though 
reduced in size. 
Fic. 5. Fusing cells with the small conjugation pore just formed. 
7 Ractsorsxr M., Uber den Einfluss dusserer Bedingungen auf die Wachstums” 
weise des Basidiobolus ranarum. Flora 82:107-132. figs. II- 1896. : 
very much 
