278 



A RACE OF FLOWERLESS PLANTS. 



leaf or stem on which they grow, or imbedded in it, as 

 do the winter spores of the grape mildew. The leaves 

 are blown about by the wind, or perhaps 

 make voyages on a stream of water. 

 Rusted straw is gathered up and trans- 

 ported to another place with the spores 

 of the fungus attached. 



Spores which have the power of mov- 

 ing in water have been mentioned. 

 There are also some fungi, certain 

 smuts, which grow on submerged plants 

 and whose spores must be disseminated 

 by the currents. 



It is very common for a fungus to 

 have at least two kinds of spores, one 

 of which cannot survive unfavorable 

 conditions, but must germinate soon 

 after maturity or perish. The other 

 kind, the most highly developed fruit of 

 the fungus, is usually made to resist un- 

 favorable conditions. In wheat-rust, it 

 is a thick-walled spore attached by a 

 permanent stalk. The winter spores of 

 the downy mildew of the grape are im- 

 bedded in the leaf and enclosed each in 

 ^ a thick-walled and durable spore-case. 

 Pear-blight bacteria may live over win- 

 ter in branches that have been cut off 

 and produce the blight in other trees in 

 the spring. 



The ergot fungus forms a horn-shaped 

 Fig. 7. mass, in which it stores up a good quan- 

 tity of food for itself. It falls to the ground in autumn 

 and lies till spring, when growth is renewed and highly 

 developed spores are formed, which at maturity are shot 

 forth like arrows. Some are thrown upon the growing rye 

 and other grass, where they renew their cycle of growth. 



In regard to the smuts of the cereals, there have lately 

 been startling discoveries made by the German investi- 

 gator, Brefeld. He found that smut spores (of corn. 

 Fig. 9) placed in a nutrient solution, instead of produc- 

 ing tubes in the usual way of germinating, grew by bud- 

 ding after the manner of yeast (Fig, 10). The dung of 

 animals that have eaten smutty corn has been found to 

 contain similar bodies, and it is known „ 

 that this mode of growth may continue 

 indefinitely. If smutty corn is thrown 

 into a manure pile, a similar result 

 may be expected. In either case the 

 fertilizer is infected. Then the farm- 

 er scatters it over the field and corn is 

 planted. As soon as the corn comes 

 up the smut seizes upon it, enters 

 and goes through its tissues in the 

 usual way, and the result is a sooty 

 mass of spores and damaged corn. 



Different fungi get into their host 

 plants in special ways. The way corn-smut gets into its 

 host was discovered only after years of trial. It enters 

 only at the tenderest part of the very young stem when 



Fig. 9. 



the corn is coming up. When the growth of the corn is 

 fairly under way, no smut can infect it. The germinat- 

 ing secondary spore of wheat-rust gels into the barberry 

 bush by making a hole in the epidermis, 

 through which it passes (Fig. 8). Molds some- 

 times get into canned fruit and into the cul- 

 ture-tubes of the bacteriologist, where even 

 bacteria cannot get in, because the molds form 

 long slender tubes or threads which penetrate 

 through crevices, while bacteria would lodge 

 and go no further. 



In some fungi, several of the above modes of dissem- 

 ination occur, notably in potato-rot, grape-mildew and 

 their allies. Figure 4 represents one of the fruiting fil- 

 aments of the potato-rot fungus, with spores on the tips 

 of the branches. During a dry afternoon these threads 

 become dried up and twisted, somewhat like a micro- 

 scopic shred of cotton. A very little moisture is suffi- 

 cient to be absorbed and render them turgescent again, 

 and in absorbing the water they quickly untwist, and 

 the movement throws off the spores in all directions. 

 There is no reason to doubt that they float easily in 

 the atmosphere and may be carried a considerable dis- 

 tance, especially if the air is laden with dew or fog. 

 The latter conditions are especially favorable to germi- 

 nation, for the spores gerrninate in water in this way : 

 the protoplasm inside the spore divides up into several 

 portions, each of which becomes a motile spore (Fig. 5). 

 They all pass out through a smalj opening in the tip of 

 the spore, and by means of their two cilia move about 

 rapidly in a drop of water (Fig. 5). At length they 

 come to rest and germinate by sending out a tube, which 

 penetrates through a stomate into the interior of the po- 

 tato leaf. Figure 6 represents a resting spore of an al- 

 lied species, in several stages of germination. It is pro- 

 tected by a thick-walled spore-case, which enables it to 

 survive the winter, and at the proper time it germinates 

 in the same manner as the summer spores just described. 



Conclusions. Burn fallen leaves of diseased plants 

 and branches cut from 

 blighted pear trees. 



Do not allow moldy 

 or spoiled food to stand 

 about the house, scat- 

 tering spores. Keep 

 free from molds and 

 germs of all sorts, or 

 get rid of them at their 

 first appearance. 



Cut out your corn- 

 smut before the sooty 

 mass is exposed to air. 



Do not feed smutted 

 grain or fodder to cattle, nor throw it into manure heaps, 

 nor put manure containing smut spores on grain fields. 



Practice rotation to avoid infection from fungi in the 

 soil, in the fertilizer or on stubble, leaves, etc. 



Fungicides are best applied on a dry day, when the 

 only water that touches the spores is the poisoned water. 

 Harvard University . A. B. Seymour. 



Fig. 10. 



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