M0loid»6 



digested away; at any rate, they disappear. There is a flom.ng together 

 of adjacent cells to form what is known in the literature as "giant 

 cells." It is also characteristic of the cells in the region of inva- 

 sion to show nuclei with the nucleoli beginning to swell. The nuclei 

 always stain densely when brought under the influence of the nematode's 

 secretions. Another thing that happens in the tissues of a developing 

 root around the nematode is that the development pattern of these cells 

 is retarded or stopped. Thus, they may never develop into the structures 

 they vrould have nomially. 



There is a tendency for new roots to form at the region of invasion, 

 particulary in the case of I'leloidogyne hapla . It is not so pronounced 

 with the other root-knot nematode species. In fact, I do not know if in 

 some of these cases many more roots than normal are formed. 



Cross-sections of the giant cells, on which the parasites feed and from 

 which they get their food primarily, show that the nuclei are large. 

 The nuclei disintegrate and disappear as the giant cells get older. 

 Giant cells formed by the fusion of a few cells have fewer nuclei than 

 those formed by fusion of numerous cells. -"- 



The parasites enter the root tips — most of them do this, but not all by 

 any means. It is the favored place of entry. They take up their 

 position in undifferentiated tissue; and as the root matures, the tissue 

 surrounding the parasites differentiates into the vascular elements and 

 so forth, while the tissue immediately surroTonding them is entirely 

 undifferentiated. It is on this tissue, of course, that the oarasite 

 feeds. 



In the first place, the reason that the larvae, in the tomato root with 

 which I was working, did not infest the roots is that they could not if 

 they had wanted to. They would have nothing on which to feed. The 

 cells had already matured. The roots were beyond the stage at which 

 the nematodes could either retard their differentiation and keep them 

 in a condition whereby they would supply the parasite with food, or would 

 contain enough food to maintain them, even if they were able to feed on 

 it. In other words, in these cases, it is necessary for the parasite to 

 influence the normal maturation of the root tissues. Thus, in the case 

 of those roots where the larvae fail to develop, I suggest that the 

 reason they fail is because they are unable to influence the normal 

 maturation of the root tissues. The root tissues go on and develop in 

 an almost normal manner, and the parasites die of starvation. 



I had thought once that the reason the parasites died Xiras because they 

 killed all the tissue around their heads in the region of invasion. 



•itJCditor's note: This was the end of that portion of the talk bas'^d on 

 discussing features to be seen in the lantern slides. 



