THE MONTHLY BULLETIN. 743 



weather the small worms or larvge may issue within two days after 

 the eggs have been deposited, much longer being required in cooler 

 weather conditions. 



The Larvae.— The larvie upon hatching either establish themselves 

 in the host plant in which they have emerged, or as is more often the 

 case, leave the host and enter the soil. This is the only period during 

 which the worms' move to any great extent in the earth, where they 

 either remain for some length of time or may immediately seek out a 

 favorable root in which the various changes in development take place. 

 The nematodes, in most cases, become completely buried in the plant 

 tissues, establish themselves in the soft cellular structur'^ )f the rootlet 

 which is rich in its food supply, and from which the worm readily 

 draws its food. The head (Fig. 39-4-7) is provided with a boring 

 apparatus consisting of a sharply pointed spear (Fig. 39-t-7.s) which is 

 located in the mouth : this arrangement not only aids in food getting, 

 but is a valuable tool in battering through cell walls before it becomes 

 definitely located. 



The two sexes during development are indistinguishable up to fifteen 

 or twenty days, both being spindle-shaped. In the mottling of the 

 skin at this time there is a marked change in the case of the female, 

 especially in the posterior region of the body, which no longer pos- 

 sesses a tail-like appendage. Fertilization undoubtedly takes place 

 soon after this moult, for many radical changes in shape and structural 

 organization of the worm take place, and the eggs begin to develop. 



Adult Female. — The fertilized female (Fig. 394-.1) increases rapidly 

 in breadth, becoming a pearly white, flask- or pear-shaped individual. 

 This is the type of organism one is most likely to see in breaking open 

 a swelling or knot on a root-infested plant. This creature is far from 

 being worm-like in appearance, and would be overlooked by one not 

 versed in the life history of the eelworm. 



Adult Male.— In shape the adult male worm is much like that of 

 the larva (Fig. 394-4), being decidedly spindle-shaped in outline. 

 The male does not inflict nearly as much damage to plant tissues as the 

 female, and its purpose in life seems to be only that of fertilizing the 

 female for, according to Bessey, after this function has been performed 

 it is quite probable that the worm takes no more food. He reports 

 finding numerous moving males with the alimentary canal reduced to 

 such a condition as to be functionless, and the body cavity filled with 

 disorganized granular masses, with the exception of the reproductive 

 system, which is intact. 



Control Measures. 



The prime factor in the control of root-knot is the cost, and this is 

 dependent upon the kind of culture to be treated, whether hothouse 

 plants, intensively cultivated fields, or the ordinary products of gen- 

 eral farming. Thus, for example, we could afford to place a consider- 

 able sum upon treating high-value plants segregated in a greenhouse, 

 when we could not afford to similarly treat a general crop growing in 

 the fields. 



