3>4 



FUXGI 



of simple germination by the emission of a germ-tube is manifest. The 

 example of i'hytophthora infestans (de By.) illustrates this. The acro- 



genously-formed zoosporange pro- 

 duces zoospores in pure water 

 containing free oxygen in fair 

 amount. In nutrient solutions, on 

 the other hand, no zoospores are 

 formed, and the potential zoospo- 

 range simply emits germ-tubes. 

 (Termination of spores, however, 

 takes place characteristically in 

 fungi by the emission of gerin- 

 tiihes under conditions of tempe- 

 rature, moisture, and the like presently to be discussed. Germination 

 by the formation of sproiit-ceUs^ however, occurs in a number of forms. 



Fig. 277. — Zoosporanges o^ PhytophtJwra in/esinfis 

 de By. a, division completed ; b, escape of zoo- 

 spores ; c. free zoospores ; d. spores come to rest 

 and germinating (x 350). (After de Bary.) 



Sexual Reproduction. 



This subject is incidentally so fully discussed under the different 

 groups, that nothing need be said here beyond calling attention to the 

 fact that it falls under the same types as in Algse. Such a form as 

 Polyphagus may, however, be mentioned since it exhibits a type apart 

 from ordinary isogamous or oogamous reproduction. 



r 



Conditions of Germination. 



Spores may be divided into 

 two categories with reference 

 X to their power of germination, 

 viz. those, by far the majority, 

 which are capable of germina- 

 tion from the time of maturity, 

 and those which must undergo 

 a period of rest. Of the first 

 kind a considerable number, 

 generally sjjeaking thin-walled 

 watery spores, sporids, or zoo- 

 spores^ do not retain this power 

 for more than a period measured 

 by hours or days. The condi- 

 tions under which they are kept 

 are, as will be expected, of importance in this respect. Many spores 

 retain the power of germination for a long period if kept in an air-dry 



Fig. 278. — Ascospores of Helvella escnh'uta Pers. 

 Stages of germination in order of letters ( x 390). 

 (After de Barj-.) 



