354 



A RACE OF FLOWER LESS PLANTS. 



Fig, 



Ergot. 



and more erect stems, an effect resembling that of in- 

 sufficient liglit, as upon vines on the shaded side of a 

 trellis, or potato sprouts in a cellar. The scab fungus 

 may retard growth on one side of 

 an apple or pear, while the unaf- 

 fected side continues to grow. 

 The mildew so common on plants 

 of the mustard family often con- 

 tracts the leaves of pepper-grass, 

 but causes considerable swellings 

 in the stems of a nearly related 

 plant. An iwohasidiiun which 

 grows on the leaves of blue- 

 berry bushes, contracts them ; 

 other forms of the fungus grow- 

 ing on the allied azalea and 

 andromeda produce inflated 

 sacs often several inches in di- 

 ameter. Many other fungi 

 cause swellings and sometimes 

 further distortions of the stems 

 and leaves on which they grow. 

 The swelling is usually composed 

 in part of the abnormally mul- 

 tiplied cells of the host plant ; 

 this may be seen in the "curl" 

 of peach leaves, the smut of corn ' 

 (Fig. 7) and the common "cedar apple" (Fig. 6) 

 which grows on red cedar trees. Another fungus of the 

 "cedar apple" group, growing on the trunks and 

 branches of white cedar, causes swellings, of which 

 some become as large as a man's head. 



Injuries caused by fungi are not confined to the green 

 parts of plants ; woody stems, roots, flowers, seeds and 

 fleshy fruits all have their parasites. 



One of the slime-molds attacks the roots of cabbage, 

 causing the disease known as "club-root." The black 

 knot of plum trees is a familiar example of diseased 

 and distorted stems. A certain fungus attacks the flow- 

 ers of the blackberry and distorts them so that they ap- 

 pear double ; and the disease is known as ' ' double 

 blossom." Various kinds of smuts are noted for at- 

 tacking only certain organs or parts of their hosts ; one 

 on the plants of the pink family fruits in the anthers ; 

 the smut of wheat destroys the ovary ; the bunt of 

 wheat destroys the interior of the ovary without much 

 affecting the outward appearance ; other species grow- 

 ing on the troublesome grass-weeds, sand-bur and 

 finger-grass, destroying the entire inflorescence ; but one 

 on fox-tail, while destroying the ovaries or seeds, pro- 

 duces almost no distortion. Corn smut is quite excep- 

 tional among the smuts, in that it grows and fruits on 

 all parts of its host except the roots. 



The young ovary is remarkably affected by the action 

 of certain fungi. 



The ergot fungus replaces the young ovary of rye by 

 a horny mass as shown in Fig. 4. Plum pockets are 

 ovaries of a plum tree converted into inflated sacs by 

 the action of a species of taphrina (Fig. 5) ; the smuts 



mentioned above and others attacking ovaries and seeds 

 convert them into a mass of powdery spores. One of 

 these found growing on a smart-weed is very beautiful 

 under the microscope. The scab-fungus, attacking the 

 newly formed fruit of the pear, kills it and it drops off. 

 Many leaves of various plants (e. g. of the currant, 

 Fig. 2) fall prematurely when attacked, apparently by 

 a process which, while abnormally induced, is yet simi- 

 lar to that which promotes the falling or leaves in 

 autumn. Contrasted with premature ripening we have 

 retarded development, diseased parts remaining green 

 while healthy parts have become brown and dry with age. 



Ripe fleshy fruits are more liable to the attacks of 

 fungi than any other vegetable productions. The fun- 

 gus may injure their quality or only their appearance 

 and market value. This is true of the scab-fungus of 



apples and 

 pears. Some 

 fungi attack 

 fruits only 

 while growing, 

 attached to the 

 tree; others, 

 like the potato 

 rot, attack the 

 growing plant 

 and continue 

 their ravages 

 in the harvest- 

 ed product. 

 Some of the 

 common sapro- 

 phytic molds of 

 the household 

 become p a r a- 

 sitic when op- 

 portunity is 

 offered, as 

 mucor upon 

 strawberries. 



In the field 

 and orchard, 

 valuable plants 

 are frequently 

 liable to infec- 

 t i o n from 

 others of less 

 value; wild 

 plums breed 

 black-knot for 

 cultivated 

 plums, wild 

 grapes and 

 Virginia creep- 

 er have mil- 

 d e w s whose 

 spores may be 

 carried to the 



Fig. 5. Plum Pockets. finest varieties. 



