436 INSECTS AFFECTING VEGETATION 



may be obtained by studying these common molds; that on a dis- 

 carded melon rind will show the parts above described, and by the 

 use of a microscope we may learn that the rounded, ball-like enlarge- 

 ments just mentioned consist chiefly of small bodies that are ca- 

 pable of growing into other fungus-threads. -Such minute parts ca- 

 pable of germinating and again producing the fungus are called 

 spores. Most spores are very minute and are not heavier than the 

 other dust particles carried by the wind. The spores of fungi are the 

 means by which these are most commonly reproduced, somewhat 

 after the manner that the higher plants about us are reproduced by 

 their seeds. 



"While we have cited the bread mold as a good illustration to 

 show the structure of a fungus, it is not a parasitic fungus ; a mold 

 or like growth which lives upon decaying material is called a sapro- 

 phytic fungus. To this same belong the mushrooms or toadstools 

 that may be found in manure piles, in the woods and in orchards; 

 the fact that we find them in such places shows that there is decaying 

 organic substance at that point, upon which these plants may subsist. 

 A like condition is found in the shelf-fungi on old logs and stumps, 

 on the under surface of which we may write our names. Yet if we 

 will use a hand lens we may often discover this under surface to be 

 but a network filled with small openings or pores from which the 

 spores of the fungus will in time escape. In like measure the spores 

 of mushrooms are found in similar canals or upon the sides of the 

 gills beneath the cap of this sort of fungus. The bacteria, or fission 

 fungi, are one-celled plants multiplying by division and by spore 

 production ; with bacteria evident mycelium is lacking and they are 

 structurally lower in the scale of plant life than fungi provided with 

 a mycelium. Bacteria are both parasitic and saprophytic. But to 

 return to parasitic fungi : 



PARTICULAR FACTS ABOUT PARASITIC FUNGI. 



Like the bread mold, or the other fungi just mentioned, para- 

 sitic fungi consist of a growth of threads or hyphae (singular, hypha) 

 which do the necessary work of getting food for the parasite; these 

 also in due time give out certain branches destined to bear spores, 

 somewhat after the manner that the pear tree has flower clusters, or 

 the wheat plant forms its dense spike of bloom, both of which are 

 especially designed to produce seeds from which wheat plant and 

 pear tree may in turn be grown. The essential parts of a parasitic 

 fungus are these threads, or hyphae, and the spores produced by 

 them. The hyphae of the fungus taken collectively are called the 

 mycelium, which consists of threads that produce no spores (sterile 

 hyphae) and of those destined for spore production (fertile hyphae). 

 It is to the food getting qualities of the hyphae that the fungus owes 

 its continual existence, and they in turn arise from a spore or directly 

 by the growth of some fragment of fungus-thread, as the Carolina 

 poplar may be grown from a cutting. Yet, while all parasitic fungi 

 are made up of these few parts, the differences in form and apparent 

 structure among the several groups are very marked ; differences exist 

 as to the thickness of the hyphae whether or not the threads are di- 



