On Teleutospore Germination. i 3 
As these conclusions are based on observations made on three 
genera of the Uredineae and as they explain completely the diver¬ 
gent results obtained generally by other observers, there seems very 
little doubt that they hold good for all the members of the group. 
The varying lengths of the promycelium hitherto described would 
then be accounted for by the varying thickness of the stratum of 
water through which, in the different experiments, the hyphae had 
to grow before reaching the free air. 
As the sporidia depend largely on the wind for their dispersal, 
the close connection between their formation and the presence of 
free air is not unexpected, especially as such a relation has been 
exactly described for the sporidia formation of Tilletia. If a spore of 
T. tritici germinates under water, the germ-tube grows until it 
reaches the air, and then only are the sporidia produced at the apex. 
The promycelium is thus shortest when grown in moist air ; and when 
grown in water, of varying length according to the depth of the 
layer to be traversed (see Brefeld, p. 198). The agreement with 
the behaviour described for the promycelium of the Uredineae is 
therefore exact. In Ustilago , on the other hand, the sporidia are 
freely formed while the promycelium is submerged. 
It is curious that this exact relation, apparently so easily ascer¬ 
tainable, should in the Uredineae require definitely stating; one can 
hardly believe that it has been overlooked by all the workers on 
teleutospore germination, but no suggestion of it could be found in 
botanical literature except the statement of De Bary (p. 281) “The 
simple tubes which may develop from the [teleuto] spores of 
Endophyllum when they are placed under water do not become 
promycelia, and are, as far at least as we at present know, incapable 
of further development.” This would appear to show that De Bary 
recognized that in Endophyllum at least, air was necessary for the 
formation of the sporidia, but it remains an isolated statement 
made in relation to the question of the stages of complexity 
of development of the Uredineae. Tulasne (p. 127) and De Bary 
(p. 350) recognized that teleutospores placed in water germinate 
with more difficulty than those in moist air, but neither makes 
any reference in this connection to sporidia formation. 
As was mentioned above, germ-tubes produced in water con¬ 
tinue to grow, usually in a more or less straight line (without 
showing any chemotactic attraction towards the surface of the 
drop), but in one case the apex of a long submerged tube had 
become divided into four cells (fig. 6), which bore some resemblance 
