DKTAILS OF STEM KELWOllMS. 



51 



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. 



Fro. 4. Anterior portion of a Tijlenchus devastutrix, taken from a Wheat-plant ; 

 magnified -140 times. 



Fig. 5. Eelworms from Hyacinth, dried and rolled together. 



Figs. C & 7. Eggs of T. dcvastatrix, showing an early and late state of forma- 

 tion 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 enormously magnified ; exact amount is given above 

 of enlargement of figs. 1, 2, .3, and 4, and amount of enlargement of figs. 6, 7, and 

 9 may be estimated by comparison of size of fertilized egg shown at ?;i within 

 female Tylenchus, fig. 1. 



With regard to dimensions of this species of Eelworm, — these have 

 previously been given; but during the autumn of last year (1894), in 

 the course of some investigations regarding a curious observation of 

 this species found in a locality in Kent (see p. 52), Dr. Ritzema Bos 

 was good enough to place in my hands a list (from his own personal 

 researches) of maximum and minimum length of males and females of 

 Tylenchus devastatrix in various of the plants which they ordinarily 

 infest, together with the following note of result of measurement : — 



"Upon an average, the Tylenchus devastatrix was — in Secale, 1*19 

 mill, (males), and 1-26 (females); in Hyacinthus, 1-43 mill, (males), 

 and 1-2G (females) ; in Allium, 1-57 mill, (males), and 1-54 (females). 

 Those in Oats, Clover, and other plants also varied between 1-18 and 

 1-60 mill, in length." * 



Turning now to the practical side of " Stem Eelworm" infestation. 

 Besides its presence in Pi.3'e, Hyacinth, and Onion-bulbs, as above- 

 mentioned, in which it occurs especially on the Continent of Europe, 

 we have it here only too commonly in various kinds of plants, and 

 causing various forms of diseased growth, as that like miniature Pine- 

 apple tops in Carnation- shoots, thence called the " Pine-apple " 

 disease, and the stunting and distortion of the plant and pods of 

 field Beans which is occasionally met with.f But the best known 



* As trustworthy identification of this and other species of Eelworms depends 

 on the correctness of excessively minute microscopic powers, and not only much 

 knowledge, but much experience of the observer, I have never yet myself given any 

 definite opinion for publication as to species of Nematoid worms without submitting 

 my identification to the verification of an expert, and almost always to the excellent 

 knowledge of Dr. J. Eitzema Bos. — Ed. 



t For figure of this from life, with description of attack, see my ' 14th Annual 

 Report on Injurious Insects,' -p-p. 17 — '21. 



E 2 



