8o 



A RACE Oh FLOWERLESS PLANTS. 



Fig. 



All that is seen of a mushroom above ground grows 

 for the purpose of bearing spores. The vegetative part 

 is the spawn in the soil. The stem comes up bearing 

 the cap ; the under surface of the cap is lined with gills ; 

 the surfaces of the gills have many special (microscopic) 

 cells, which stand out perpendicular to the surface ; each 

 of these has at its tip four projecting points, and each 

 point bears one spore (Fig. 5). The purpose of the spore 

 is the same as that of the seed— to produce a new plant. 

 The downy grape mildew has two kinds of spores : one 

 formed inside the grape 

 leaf, the other outside. 

 The mycelium is inside 

 the leaf. It produces spe- 

 cial branches, which grow 

 out through the breathing 

 pores of the leaf, then 

 branch out like micro- 

 scopic trees, and bear a 

 spore at the tip of each 

 branch. It is this growth 

 that is so abundant as to 

 form a white down on the 

 under surface of the leaf, 

 whence the name downy 

 mildew. These are the 

 summer spores. In time 

 of active growth there is a 

 5' fresh crop of them every 



morning. They germinate quickly, being disseminated 

 in drops of dew or rain, but if the conditions of the ger- 

 mination fail they die soon. Here is a place to supply 

 a remedy, or rather a preventive, to check the spread of 

 the fungus. 



Spores of the other kind are formed in the substance 

 of the leaf singly. They have a thick, hard coat, which 

 fits them to live over winter. Here a remedy again : 

 burn the fallen leaves in autumn. 



Wheat rust has three kinds of spores, 

 and one kind, curiously enough, does not 

 grow on wheat, but on barberry. Of this 

 more may be said at another time. On 

 the wheat itself the summer spores con- 

 stitute what is called red rust, and the win- 

 ter spores constitute black rust. 



The number of spores produced by fungi 

 is very great. On a single infested wheat 

 plant or grape leaf there are millions, and 

 each spore, under proper conditions, is able 

 to spread the disease. Of course, a large 

 pi-oportion perish, just as among seeds and 

 pollen grams belonging to flowering plants. 

 How many thousands of millions of spores 

 must be contained in a great swelling of 

 smut on a cornstalk, or in a giant puff-ball 

 three feet in diameter, both of which are 

 filled with fine dust, each particle of the 

 dust a spore ! A cubic inch of space is large enough 

 to contain more than eight thousand million corn-smut 

 spores. 



Spores, of course, germinate and grow in the same 

 general way that seeds do. A spore most commonly 

 protrudes a filament of mycelium, which by continued 

 growth forms all the mycelium, all the vegetative part 

 of the mature fungus. Fig. 6 shows a germinating spore 

 of the red rust of wheat. 



How does the fungus get into the plant ? In some 

 cases, for example, in the potato rot, the spore sends a 

 slender tube through a breathing pore of a leaf, the tube 

 enlarges inside the leaf, and all the semi-fiuid proto- 

 plasm passes in. Once inside it can make its way 

 almost anywhere among the soft tissues. Corn-smut 

 gets in when the corn is coming up ; then it grows all 

 through the green parts, showing no signs of its presence 

 for weeks or months, but at length bursting out with a 

 mass of soot-like spores in almost any part of the 

 plant. The absence of leaf-green in fungi demands 

 more than a passing notice. It is the most important 

 thing about a fungus. If fungi were green we would 

 hear nothing about fungus diseases of plants, wheat 

 would never rust, potatoes would never rot, bread would 

 never mold, nor clothing mildew. Foul drains would 

 cease to be dangerous, or cease'to exist. On the other 

 hand, we would have no yeast bread, no vegetable mold 

 to enrich the soil, fallen branches and leaves would ac- 

 cumulate indefinitely in the forests without decay. 



Why ? Because if fungi were green they would take 

 their nourishment from the soil and atmosphere, as green 

 plants do, and would not live on organic matter. Their 

 lack of leaf-green forces them to depend upon something 

 that some green plant has produced from the soil. In 

 this respect fungi are like animals. The question of 

 respiration comes in here also. Animals breathe in the 

 oxygen of the atmosphere and exhale carbonic acid. 

 Fungi and all other plants do the same thing. This is a 

 universal characteristic of life and growth. Green plants 

 are peculiar, in that they do this and the opposite thing 

 also. All organisms consume food, only green plants 

 produce it. The process of produc- 

 tion is necessarily the reverse of con- 

 sumption. On the one hand, consump- 

 tion, respiration, oxydation or burn- 

 ing — oxygen consumed ; on the 

 other, assimilation, deoxydation or 



rning — oxygen set free. In 

 line green plants take in car- 

 ; acid and give out oxygen. We 

 see also why fungi can grow and 

 complete their life in darkness as no 

 other plants can— a distinction which cannot fail to in- 

 terest the observing horticulturist. 



Harvard Colles'e. A. B. Seymour. 



