198 



CIVIC BIOLOGY 



thread, the hypha, which in some fungi is tubular and in 

 others is septate, that is, composed of cells end-to-end. Hyphge 

 branch continually and seek the cracks and minutest pores, 

 and so are able to burrow and digest their way into all sorts 

 of apparently solid substances. The hyphae are functionally 

 of two kinds : first, the threads that burrow and feed in or on 



FIG. 97. Two common molds in different stages of growth 



A, B, C, a common blue mold, Penicillium; A, spores germinating; B, as seen 



growing in vial of liquid ; C, aerial (or fruiting) hyphae more highly magnified ; 



D, E, F, similar stages in the growth of a black mold, Rhizopus 



the food material the vegetative hyphae ; and, second, the 

 fruiting hyphae, which grow out of the mass into the air (or 

 water in case of the water molds) to form the various kinds 

 of spore-bearing organs. These ideas are fundamental to 

 control of fungi, and we should be sure that they are entirely 

 clear in working out the following experiments. As we aim to 

 destroy weeds before they go to seed, so we must adopt meth- 

 ods to prevent our fungus enemies from ripening their spores. 



