192 A TEXTBOOK OF THEORETICAL BOTANY 



On germination the spore gives rise to a single spindle-shaped swarm cell, 

 which is provided with two apical flagella, one of which is longer than the 

 other (Fig. i8i). The time taken for the spores to germinate varies with the 

 species, but laboratory tests by growing them in a sugar solution show that 

 while some species, e.g., Reticiilaria lycoperdoji, may germinate in a few hours, 

 others take two to three weeks to produce swarm cells. After liberation 

 from the spores the swarm cells fuse in pairs at once and give rise to 



Swarm cell 



Fig. i8i. — Reticiilaria lycoperdon. Germination 

 of spores to release swarm cells. 



binucleate zygotes or myxamoebae, from which a new plasmodium will 

 arise (Fig. 182) in which the nuclei fuse in pairs, a process called karyogamy. 



In the genus Ceratiomyxa mentioned above (Fig. 183) the development 

 is somewhat different, for the plasmodium lives internally within dead or 

 decaying wood and only produces fine processes termed sporangiophores 

 externally. These bear minute sporangia which are oval in shape and pure 

 white in colour. It is said that each sporangium, which is frequently referred 

 to as a spore, gives rise to about eight swarm cells. The individual spores in 

 other genera produce only one. 



Species of the Myxomycetales are very common among dead wood and 

 leaves in damp woods and are extremely beautiful objects. Though the 

 individual sporangia are often no larger than a pin's head they are generally 

 produced together in sufficient numbers to be seen easily. A careful search 

 of any damp wood or damp pile of sticks or straw will be certain to yield a 

 number of different species. 



Plasmodiophorales 



The Plasmodiophorales are parasitic Archimycetes in which the plas- 

 modium lives in the cell of a higher plant. By means of fragmentation the 



