Hot^r: 



but rather are concerned with a complex of substances. Some support is 

 lent to this by the fact that in some species there may be stimulation 

 due to such materials as inorganic salts. I:ost of this kind of uork 

 has been done with H. sc2iachtii. If you use such a substance as common 

 salt or even such an unlikely substance as mercuric chloride, you will 

 find that you can get at certain concentrations quite a noticeable in- 

 crease in hatch. Of course, as concentrations get too strong the hatch 

 drops off to zero. You can get this result vjith a variety of things 

 such as urea, amino acids, and some sugars. So you see that there are 

 a number of materials v;hich one might find in the rhizosphere, mercuric 

 chloride excepted, and which one might expect to contribute to the hatch- 

 ing. I would like to mention here we have tried a substance found by 

 two American workers which they have called galactinol, which they have 

 isolated from sugar beets. In their paper they have said this is one, 

 if not the, hatching factor. In England we have tried this chemical 

 with our sugar beet nematode and have found no evidence of it having any 

 hatching value at all. Its effect is quite indistinguishable from that 

 of water. Now it ma^' be that we are wrong and they are right, or that 

 we are both right. I supoose a little more work is indicated. VJhenever 

 you get differences in work of this tyoe, it does not mean that the 

 other chap is wrong, rather it means more investigation is necessary, 



TPEMDS; Dessication 



Another trend within the genus is the ability of ;^dthstanding des- 

 sication. Some species, like H. rostochiensis , can out up with quite a 

 lot of drying. These cysts when extracted from the soil can be stored 

 almost indefinitely and hatching will occur if they are given a suf- 

 ficiently long soaking in v;ater, which may be as long as fifteen days 

 or so. Almost anything you do to H. schachtii seems to reduce its hatch- 

 ing. For example, lowering the oxygen content in the water and dessi- 

 cation. H. schacht ii, particularly our H. schachtii , doesn't seem able 

 to stand up under dessication as does H. rost ochiensis . Our H. sch achtii 

 may be different from yours. Drying appears to kill H. major . You must 

 therefore be very careful in doing work with hatching tests. You must 

 not use glaring lights which may lieat them and do not do any other thing 

 which may effect their hatching. These considerations ^T-f^ Quite important, 



HOST PAHGE S 



Now I would like to turn to host ranges. The systematist is 

 obviously a very important man; he tells us which nematodes we have. 

 But from the farmers point of view, the ii:an who is more important is the 

 one who can tell us what the host range is. Economically, the host 

 range is, I think, of paramount importance. Among the Heteroderas I 

 think we can divide them I'oughly into two types. There are those like 



