58 BOTANICAL GAZETTE | JANUARY 
poisonous excretions of plants, but all excretions may have their 
role to play regarding infection. At any rate, from the point 
of view of the fungus, a further study of chemotropism, of stimu- 
lants to germination, and of the inhibition of germination and 
growth by injurious substances cannot fail to lead us somewhat 
farther toward a knowledge of parasitic attack. 
RESTING STAGES AND DRYING-OUT OF SPORES. 
It is well known that seeds of certain phanerogams do not 
readily germinate on reaching maturity. From the researches 
of Weisner and others with rather peculiar phanerogams, it is 
seen that this resting period is not merely due to an absence of 
the best conditions, but that the element of time, as far as we 
know, is absolutely essential. Whether we may in some cases 
substitute for this element of time artificial changes of condition 
is mostly a matter of conjecture. 
The same remarks will hold in a general way pit the so-called 
resting stages of fungi. For the maturity of the spores of the 
Peronosporaceae and many of tlie teleutospores of the Uredineae, 
as examples, a certain resting period is indispensable. From 
the cytological studies of Wager,”? it would appear probable 
that in the case of Cystopus candidus the maturity of the oospores, 
so far as the external appearances are concerned, does not 
denote the maturity of the zoosporangium with reference to the 
full quota of nuclei as a basis for the formation of zoospores. 
It appears that a resting stage must intervene before the final 
divisions of the nuclei. 
Teleutospores of Puccinia graminis germinate best when they 
have been subjected to all the changes of the winter months. 
Observations on the presence of a certain coloring matter in the 
walls of such spores led Dietel?3 to attribute to this certain prop- 
erties for the prevention of the germination, and for protection 
against unfavorable conditions. DeBary** has found that the 
teleutospores of the previous harvest cannot be brought to germi- 
7? WaGER, H.: Reproduction of Cystopus candidus. Ann. Bot. 10: 245-339: 
"3 DIETEL, P.: Flora 74: 151. 1891. 24 DEBaryY, A.: lL. c. 



