DEVELOPMENT OF PLANTS 



135 



a foot in diameter and from spherical to cylindrical and cake-like 

 masses. Not infrequently they are of great beauty owing to their 

 coloration and lace-like structures. These small sacs or spor- 

 angia (sing, sporangium) as they are commonly called, repre- 

 sent but one stage in the life of the slime moulds. If we begin 



Fig. S7. 



Fig. 87. The sporangial stage of two common slime moulds : A, Lyco- 

 gala. B, Arcyria. C, sporangia rupturing, hair-like structures (the capil- 

 litium) and spores protruding. D, sporangia emptied. 



Fig. 88. Open types of sporangia: A, Stemonitis, at left a single spo- 

 rangium enlarged, showing net-like structure formed by capillitium radi- 

 ating from the central stalk of the sporangium. B, Cribraria. 



with an examination of the dust that floats away from these 

 sacs every time they are tapped, the life history will be found to 

 be about as follows : Under the microscope the particles of dust 

 are seen to be minute cells or spores (Fig. 89, A) each provided 

 with a cell wall and containing a nucleus and protoplasm. A 

 spore is a cell that is capable of germinating under favorable 

 conditions and producing a plant. In this case it is advisable 

 when germinating the spores to place them in a nutrient solu- 



