120 ARTHUR: IMPORTANCE OF THE SPERMOGONIUM 
draws to a close, in this manner widely distributing the species. 
If no uredo occurs in the series, the aecidiospores often possess 
the power of repetition ; and if neither uredo nor aecidia occur, the 
teleutospores may act in the same way, as in the numerous species 
of the Lepto-Uredineae. 
It is worthy of note that in a complete series of spore-forms 
there is but one generation of aecidia, and that the mycelium bear- 
ing the aecidia does not continue, as a rule, to live and produce ~ 
uredospores, but comes to an end with the fruiting of the aecidia. 
The fungus is then re-established by aecidial germination. Thus 
the development is thrown into two hemicycles. One may inci- 
dentally observe that, except as an aid to heteroecism, there ap- 
pears no evident advantage to the fungus in possessing two coni- 
dial spore-forms. All the work of dissemination is equally well 
done by either one of the two forms, acting alone. 
SUCCESSION OF SPORE-FORMS. 
A. Complete series | B. Uredo wanting. C. Aecidia wanting. | D. No uredo or aecidia. 
¥ y y | y 
oO O Oo | +e) 
I I aut | aes 
III | Ill | I | ul 
The repeating spore-forms are in heavy type. 
An observation more pertinent to our inquiry is, that the 
spermogonium occurs but once in the cycle, not being repeated 
with each generation of repeating aecidia or uredo. In case the 
teleutospore takes on the conidial function it is uncertain whether 
the spermogonium is repeated with each summer generation of 
not. In Puccinia Malvacearum, and similar Lepto-Uredineae, the 
spermogonium seems to be wholly suppressed, even with the 
first generation in spring. It is unnecessary, however, for the pur- 
poses of this paper either to decide or to discuss this doubtful point. 
After this rather tedious exordium I am prepared to make the 
first of two statements regarding the taxonomic value of the sper- 
mogonium : to record its presence, and the spore-generation with 
which it is associated, gives valuable information regarding the 
probable length of the cycle. By referring to the last diagrams 
it will be clear at a glance, that if spermogonia and uredospores 
