48 THE MYXOMYCETES 



Skupienski (1920), on the other hand, believed that enzyme ac- 

 tion did not in any way account for increased osmotic pressure. 

 After observing germination among 56 species Gilbert (1928) 

 expressed the opinion that local enzyme action may soften the 

 wall in species \\'hose membrane opens by a jagged pore, as in 

 Dicty diaethaliinii phnnbeinn. The wedge-shaped cleft charac- 

 teristic of the other type of opening is t\^pified by Fiiligo septica. 



As in the germination of spores of other organisms, environ- 

 mental factors exert a controlling influence. Nearly all species 

 terminate best in decoctions of the substrata on which they nat- 

 urally occur. Smart (1937, 1938) found that all but four of 

 the 70 species and varieties which he employed could be made to 

 o^erminate in water alone. 



Some slime molds retain their viability for incredibly long pe- 

 riods. Smith (1929) germinated the spores of 21 species after 

 thev had remained in the laboratory for periods of 5 to 35 years. 

 Some are capable of immediate germination, as are Arcyria de- 

 midata, Dictydhmi cmicellatinn, Dicty diaethalhmi phmibeinn, and 

 Fiiligo septica. . Others, such as Hemitrichia serpida, do not ger- 

 minate until they have aged a year or more. 



There are two types of germination among Myxogastres, each 

 characteristic of the subclass, Exosporae or Endosporae, of this 

 order to which the species belongs. A few species of Ceratio- 

 myxa comprise the first subclass, and all other species the second. 



In Ceratiomyxa the spores (protospores) on dehmitation con- 

 tain a single nucleus, but at maturity they become four-nucleate 

 by two equational divisions. Upon germination the entire con- 

 tent emerges as an amoeboid, naked body or as a four-lobed mass 

 in which the nuclei again divide, and the protoplast then sepa- 

 rates into eight uninucleate portions, each a flagellate, pyriform 

 swarm cell. These swarmers fuse in pairs to form the zygote, 

 which increases in volume to become the plasmodium. Just be- 

 fore the delimitation of protospores, reductional division is ac- 

 complished as shown by Jahn (1908) and verified by Gilbert 

 (1935). 



In the Endosporae, many of which have been studied, the 

 spores on germination form 1 to 4 swarm cells. Gilbert (1928b) 

 studied 18 species, finding that Badhamia lilacina, B. iiiagna, 

 Fhysannn connatimi, Leocarpiis fragilis, and Miicilago spongiosa 

 form 1 to 4 swarm cells and that Physanim compressimi^ P. leu- 



