UNINUCLEATED AECIDIOSPORES IN CAEOMA NITENS, 
AND ASSOCIATED PHENOMENA 1 
By B. O. Dodge 
Pathologist , Fruit-Disease Investigations , Bureau of Plant Industry , 
United States Department of Agriculture 
INTRODUCTION 
The cytology of the mallow rust Puccinia malvacearum has been studied by 
Werth and Ludwigs (15), Moreau (12), and others. 2 Nothing was discovered 
that suggested to these investigators that the omission of the spermogonial struc¬ 
tures has any special significance whatever in the life of the rust. The discussions 
and controversies in regard to this short-cycled Puccinia have largely centered 
around questions as to time and method of infection and of over-wintering. Cell 
fusions take place in the sorus, each binucleated cell of the teleutospore becomes 
uninucleated by nuclear fusion, divisions occur and a 4-spored promycelium is 
developed. 
In describing the spore forms of species of rusts mycologists frequently state 
that spermogonia (pycnia) are unknown or wanting. A preliminary study of the 
short-cycled orange-rust, Caeoma nitens , on blackberries, has led the writer to 
suspect that the suppression of spermogonia in the life of this rust may follow as 
the result of something more fundamental than that which leads to the omission 
of the pycnidial stage by some species of the ascomycetes. In other words, if 
the facts can be interpreted in the light of phylogenetic developments, it may be 
discovered that the omission or suppression of the spermogonial stage is in reality 
of sexual significance although the spermatia in themselves take no part in a pro¬ 
cess of fertilization. A brief resume of the occurrences which led the writer to 
give closer attention to the cytological details in the growth of the orange-rust of 
Rubus may perhaps serve as a statement of the main features presented in this 
paper. 
Several years ago while growing rusts in the greenhouse for class use at Columbia 
University, the writer observed that in certain cases of infection of blackberry by 
the short-cycled orange-rust, no spermogonia were developed on plants whose 
leaves were maturing the aecidial stage. This was in striking contrast with what 
is commonly known to occur. One of the most familiar sights in this country is 
the appearance of etiolated blackberry shoots whose leaves are covered with sper¬ 
mogonia when the infected sprouts emerge from the ground some days in advance 
of the others. In reporting on the results of work relating to infection of black¬ 
berries with the “haploid” generation of the orange-rusts (8), it was pointed out 
that as the inoculated plants of the Iceberg variety began to show signs of infec¬ 
tion, no spermogonia could be found, even though the shoots were several inches 
high and the young aecidia. were beginning to develop. That this omission of the 
spermogonial stage was not due specifically to peculiarities of this host, which is 
1 Received for publication June 30,1924—issued Nov., 1924. 
1 Reference is made by number (italic) to “ Literature cited,” p. 10o8. 
Journal of Agricultural Research, 
Washington, D. C. 
( 1045 ) 
Vol. XXVIII, No. 10 
June 7, 1924 
Kev No. 0-450 
