1918] CURRENT LITERATURE 371 
species has led GREBELSKY” to undertake a study of this characteristic, in order 
to determine its constancy for given species and to discover the factors influen- 
cing the distribution of the sori. A statistical study of 42 species of rusts gave 
evidence that with few exceptions the uredinia are formed on the stomate- 
bearing side of the leaf. Especially striking illustrations are found in such 
forms as Melampsora Larici-retusae, which infects two species of willows 
S. retusa with amphigenous stomata. Here the distribution of the ur a 
corresponds to that of the stomata, exceptions occurring only in leaves on which 
the infection is unusually severe. Some cases are noted, among them Puccinia 
g/umarum, in which the sori do not occur on both — of the leaves, although 
the stomata are amphigenous. 
In a number of plants examined histologically it was found that the young 
sori always originate beneath the stomata; coating parts of the stomatal sur- 
faces with wax led to the suppression of sori. y turning leaves with amphige- 
nous stomata, but on which sori were normally produced on one side only, the 
author was able to shift the position of the sori to the other side of the leaves. 
Mere cultivation in the greenhouse induced sori normally present on one side 
of a leaf to become amphigenous. ‘This result is attributed to the absence, on 
plants grown in the greenhouse, of wax coating by which the author believes 
the formation of sori is normally suppressed on the most heavily coated side 
of the leaf. 
Some time ago, MoRGENTHALER™ showed that the production of teleuto- 
spores by rusts was determined by conditions internal to the host rather than 
by external factors. Further evidence of this relation has been brought out by 
GassNER" in his studies of the South American grain rusts. The observations 
on Puccinia triticina, P. coronifera, P. graminis, and P. Maydis all indicate 
that teleutospore formation is associated with a definite state of maturity of 
the infected organ. Particularly clear and striking evidence that seasonal 
changes have little sia was obtained in the case of P. triticina and P. 
coronifera. On plants sown at intervals throughout the year, these rusts 
regularly produce setae followed by teleutospores. In P. ¢riticina on 
wheat, production of teleutospores begins shortly before the appearance of the 
ear. This fact is particularly noticeable in varieties requiring different lengths 
of time for development. Seasonal influence is evident only in so far as it 
affects the development of the host. The teleutospores of P. coronifera on 
oats are also formed at the time of the appearance of the head, but with P. 
graminis on wheat, barley, and oats teleutospore formation does not begin 
en 
*° GREBELSKY, F., Die Stellung der Sporenlager der Uredineen und deren Wert als 
Systematisches Merkmal. Centralb. Bakt. I. 43:645-662. figs. 12. 1915. 
= ans Bort. Gaz. 56:162. 19 
ASSNER, G., Die Tslesorening der Getreiderostpilze und ihre Bedin- 
gungen, Zeitache. Bot. 7:65-1 
