“~ 
i a 
LLL AAI OEE = 


1901 | GERMINATION OF SPORES 57 
TABLE VI. 
PERCENTAGE OF GERMINATION. 


PHO. | Pertone | gecrction | decoction | 22 tims | oom 
2 Solution | 5 ze 
Puccinia Helianth 
uredos spores) 1oo— 20 25 * 50 10 * " 
Uromyces caryophi 
linus (uredospores)| 100— 100— 0 g5° 1: 200 160 ne? 








* Germ tubes very short and often ill-formed. 
DeBary and others have noted an injurious effect of nutrient 
media upon the formation of zoospores in certain Peronosporeae. 
The effect is to suppress the amount of zoosporic germination, 
and to develop germ tubes instead. Wuthrich* found the same 
phenomenon characterizing the germination of Phytophthora 
infestans under the influence of small amounts of poisons. From 
experiments with Plasmopara viticola, | have found no germ tube 
development; but many nutrient media inhibit the germination 
of the species. Winogradski and Omeliansky** have determined 
that a number of organic compounds act even at considerable 
dilutions to hinder or prevent the normal action of the nitrite 
and nitrate bacteria, and often even to sterilize the solution in 
which it was attempted to grow these organisms. Among these 
inhibiting substances are peptone and other albuminoids, 
glycerin, salts of organic acids, and also ammonia. 
We are at this time far from a rational conception of the 
most important problems concerning the relation between host 
and parasite. The resistance of species and varieties cannot be 
viewed merely from a histological standpoint, and so far as the 
problem is capable of solution, a complicated set of factors is 
to be expected. If peptone and other nutrient media may be 
injurious to the a of certain fungi, not only the 
Woruricn, E.: Ueber die Einwirkung von Metallsalzen auf die Keimfahigkeit 
der Sporen Pune ais ae Pilze. Inaugural-Dissertation, Berne, 1592. 
WinocRaDski und OMELIANSKY: Ueber den Einfluss der organischen Sub- 
Stanzen auf die Arbeit der nitrifizierenden Mikroben. Centrlb. f. Backt. u. Parasitenk. 
5°:319-343, 371-387, 425-440. 18 
