6 
CLOVER-SICKNESS. 
I 
For practical purposes, the deformed growth of the “stem-sick” 
Clover is quite enough to show the nature of the attack, but as a 
guide to what is to be searched for in cases where this altered growth 
may not be as yet sufficiently advanced to show the cause of the 
“sickness,” I give the accompanying magnified figures, which I am 
permitted to make use of by the courtesy of Dr. J. Ritzema Bos.* 
These figures give all requisite details for microscopic identification. 
Explanation of Plate. 
Fig. 1. Tylenchus devastatrix, female, taken from an Onion plant ; magnified 
200 times. 
a, spear; b, first muscular swelling of the oesophagus; c, second oesophageal 
ring ; d, e, intestine, properly so called ; e, f, rectum ; /, anal opening ; g , excretory 
pore (orifice of the lateral vessel); h , commencement of the ovary; i, ovule, with 
nuclei (or germs), not fertilized; Jc, first half of the oviduct (tube), with sperma- 
tozoids ; l, second half of the oviduct, with glands in the wall; m, anterior portion 
of the uterus, containing a fertilized egg; n, sac, with closed extremity, second 
portion of uterus; o, vulva. 
Fig. 2. Tylenchus devastatrix , male, taken from an Onion plant; magnified 
200 times. 
For a , b, c, d, e, and g , see explanation of preceding figure ; /, cloacal opening ; 
h, commencement of the testis; i, mother-cells of the spermatozoids (Spermato- 
blastes); k, cells further divided, forming spermatozoids; l, vas deferens; m, 
spicule; n, accessory piece; o, purse. 
Fig. B. Anterior portion of a Tylenchus devastatrix , not fully developed, taken 
from an Onion plant; magnified 440 times. 
For a, b, c, and d, see explanation of fig. 1. In front of the spear (a) is shown 
the labial region, and lower, at the base of the spear, the musculi protractorii leading 
forwards, and the musculi retractor ii leading backwards. The half of the oesophagus 
in advance of the first bulb, or muscular swelling (b), has a straight direction; the 
half which extends from the first to the second muscular swelling is waved. In the 
second bulb nuclei are visible. Near ( d ) the intestine begins; in the wall of this 
the separate cells are not distinguishable, because of the presence of the numerous 
drops, which refract the light strongly. 
Fig. 4. Anterior portion of a Tylenchus devastatrix , taken from a Wheat-plant; 
magnified 440 times. 
Fig. 5. Eelworms from Hyacinth, dried and rolled together. 
Figs. 6 & 7. Eggs of T. devastatrix , showing an early and late stage of formation 
of the embryo. 
Fig. 8. The young wormlet (T. devastatrix) newly emerged from the egg. 
Fig. 9. Egg of T. devastatrix before segmentation of protoplasm. 
The above figures are all given enormously magnified. For some further notes 
of measurement, see p. 7. 
* See Plates I. and II. in ‘ L’Anguillule de la tige (Tylenchus devastatrix , Kuhn),’ 
par Dr. J. Ritzema Bos, Prof, a l’lnstitut Agricole de l’Etat a Wageningen. 
* 
