400 HYPHOMYCETES 



2. ZYGOSPORES. This variety of spores is formed as follows: 

 The outer, free ends of two hyphens, or filaments, swell up and 

 become club-shaped. The clubs touch each other and the membranes 

 separating them become fused. The united clubs at the same time 

 become divided from the rest of their hyphens by two septa. In this 

 way two separate cells touching each other are formed. These are 

 called copulation cells, or gametes, while the upper part of the hyphens 

 which carry the latter are known as the carrying cells, or suspensors. 

 The partition wall, or septum, between the two gametes touching each 

 other finally become dissolved, and from the contents of the two 

 copulation cells the spore, known as a zygospore, is formed. Spores 

 are also sometimes formed from a single hyphen without the union 

 of two gametes, and this variety of spores is called azygospores, or 

 parthenospores. 



3. EXOSPORES, OR CONIDIA. These may be formed by either of 

 the following ways: In some hyphomycetes the fruit bearer at its 

 upper extremity forms a round end which becomes separated from 

 the rest of the filament by a septum. The cut-off segment then 

 assumes a round or oval shape, forming thus the first spore. The 

 end of the hyphen to which the first spore adheres repeats the process, 

 and a second spore is formed situated between the first spore and the 

 end of the hyphen. This process continues, and gradually a row of 

 spores, of which the outermost is the oldest and the innermost the 

 youngest, becomes attached to the fruit-bearing hyphen. In the other 

 method of spore formation the first spore is formed in the manner 

 just described, but then it itself divides, and this process continuing, 

 a row of spores is formed in which the outermost is the youngest and 

 the innermost the oldest. The first mode of spore formation proceed- 

 ing from the inner end of the row is called basipetal conidia formation; 

 the second, in which the new spores are formed at the outer end, is 

 known as basifugal conidia formation. 



CHLAMYDOSPORES, OIDIA, OR GEMMAE FORMATION. In this form of 

 spore formation a fruit bearer proper is not formed, but the filaments 

 of the mycelium break up into small segments. Each of these when 

 falling upon a fertile soil may form a new hyphomycete individual. 

 This mode of spore formation was first observed in a fungus known 

 as Oidium lactis, and for this reason it is also called oidia formation. 

 The small segments arising in gemmse formation often assume a more 

 marked spore character by surrounding themselves with a tough, 

 tenacious, protecting membrane. 



Resistance of Spores. The resistance of spores of hyphomycetes 

 is generally like that of the spores of bacteria, and like them they are 

 more resistant than the adult form of the organism. As a rule, however, 

 their resistance is not as great as that of bacteria, though some may 

 withstand drying out for many years. Hansen has shown that the 

 spores of certain common moulds survived after a desiccation of 

 from eight to twenty-one years. Pasteur has shown that the conidia of 



