June 15, 1914 
Citrus-Root Nematode 
225 
Tylenchulus by his simple process, and in from six to seven weeks it 
was possible to secure adult females from roots thus infested. 
The following is a typical case: On May 31, 1913, adult females, as 
well as larvae and eggs, were removed 
from the roots of a grapefruit 
seedling first infested on April 14, 
1913. As a rule, the full-grown males 
were found much earlier than the 
females; in fact, there can be little 
doubt that in most cases the infested 
water supplied at the beginning of 
the experiment contained a few males 
that were adult or nearly so. The 
gist of these experiments is contained 
in the fact that the infested water 
would contain but few, if any, fe¬ 
males that were advanced beyond 
the stages shown in figures 12 and 
Fig. 10— Pot containing Citrus seedling. A portion 
of the wall of the pot has been removed to show 
location of one of the glass brood capsules shown 
in figure n. a, Brood capsule; 6, label of same 
attached to capsule by means of a thread which 
passes down through the soil. Tylenchulus eggs 
incubated in this way often hatch out in 24 hours. 
Larvae reared on grapefruit roots in pots similar 
to that shown above become adult in six to 
seven weeks. 
13, and that the entire life cycle of the 
females under the conditions of the experi¬ 
ments was shown to be accomplished in 
six to eight weeks. 
A few words about the probable origin 
of Tylenchulus semipenetrans may not be 
out of place. As this parasite occurs in so 
many different, very widely separated Cit¬ 
rus regions and is found only on Citrus 
roots, it is a fair supposition, as before 
remarked, that it is peculiar to species 
of Citrus. The most reasonable expla¬ 
nation of its wide distribution is that it 
has been sent from point to point in com¬ 
merce on the roots of Citrus nursery stock. As this distribution of the 
parasite has probably been going on for centuries, the obvious surmise is 
that the original habitat of the parasite is that of the genus Citrus itself. 
Fig. 11.—Longitudinal section of a glass 
brood capsule enlarged 10 diameters. 
The cord at the left leads upward to 
the surface of the soil. Compare with 
figure 10. In these capsules the young¬ 
est eggs of Tylenchulus semipenetrans , 
even those removed from the uterus, 
hatch out in 24 to 72 hours when the 
capsules are placed adjacent to healthy 
roots of growing Citrus seedlings, a , 
glass tube shown in longitudinal section; 
6, thread encircling capsule, shown in 
cross section; c, finest mesh linen cloth 
held over bottom of filter capsule by 
the encircling cord b; d, layer of filter 
paper, for convenience shown black; e, 
/, disks of filter paper; g, nematode egg 
embedded in Pasteurized orange root 
detritus and soil granules. 
