740 THE MONTHLY BULLETIN. 



cultivator teeth. How efficient is this method of distribution to tlie 

 spreading of the pest in the citrus districts! Every grower has seen 

 his cultivator couie from the orchard with a bunch of root fibres 

 clinging to the machine between the shank and shovel, and as there 

 have been found as many as fifty worms on a rootlet an inch in length 

 it is quite evident, owing to the method upon which many small ranches 

 are operated, i. e., by hired teamsters with their own tools, that many 

 worms could be "sown" in a day. 



Irrigation in areas where the pest has once been established offers 

 an ideal method of distribution. The worm, though unable to live 

 any great length of time in water, finds the damp, shady, irrigated 

 orchard most advantageous for a successful existence. 



Mr. Thomas found that the eelworm of the orange did not produce 

 knots and swellings as had been previously reported, and for this 

 reason, no doubt, the worm has been transported widely and unknow- 

 ingly on infested nursery stock throughout the greater part of the 

 citrus growing districts. Orange rootlets infested with the pest, 

 though not possessing the characteristic swellings, do not appear 

 healthy, as Fig. 396 will show. The cortex is irregular and rough, 

 sometimes showing spots that appear like small bits of exuding gum. 



Effect Upon the Host. 



The direct effect of the worm upon the plant is at the point of con- 

 tact, the result being the formation of knots, swelling and general 

 disorder of the normal function of the root tissue. This displacement 

 and disarrangement of tissues, results in a complete disorganization of 

 the cellular makeup and arrangement, often to such an extent, that 

 certain distinctive tissues with definite functions become entirely seg- 

 regated from cells of the same kind. 



In the case of the strawberry plant shown in Fig. 85)2 the rootlets 

 show a distinct enlargement at "the point of infestation; here, through 

 the disorganization of cell tissues, a constriction is formed ; food prop- 

 erties can no longer pass, and the rootlet beyond the swelling becomes 

 functionless, and ultimately dies. When the roots of a plant become 

 badly affected the direct influence upon the plant must be felt, and as 

 a result that part above ground, by assuming an unhealthy appearance, 

 will indicate the presence of some abnormal condition, the result of 

 malnutrition through the loss of necessary plant foods taken from the 

 plant by the small parasites in its root system and the reduction of 

 food-getting facilities through disorganization. 



Naturally, the condition of the plant varies directly in proportion to 

 the number of parasites which it maintains, or to the resistant qualities 

 which it may possess, so that the effect upon the many varieties^ of 

 plants is not always the same. The symptoms are much more notice- 

 able in fast-growing annuals than in trees and shrubs. Here the first 

 indications of disease are the drooping and yellowing of the foliage. 

 The plant in a short time becomes limp, the stems wilt and the hot 

 rays of the sun soon burn up the weakened, poorly nourished tissues. 



When vigorously growing plants suddenly turn yellow and die, 

 immediately exammethe roots, and the cause of the sudden death of 

 the plant may usually be established by careful- observation. The tell- 

 tale, knotty, disarranged root system will indicate the presence of the 



