MARCH 



IRISH GARDENING, 



35 



earth, in sea-sand, and elsewhere, feeding- for 

 the most part on decaying- organic matter. 

 Only a few kinds are injurious to living plants, 

 and in some cases, at least, these require some 

 previous external injury to the plant to enable 

 them to make their way into the soft tissues. 

 For example, Mr. R. Southern,* of the National 

 Museum, Dublin, has lately described a new 

 species of Rhabditis {R. brassicce) which occurred 

 in enormous numbers in rotten 

 turnips from Co. Westmeath. 

 " When placed in contact with 

 a cut surface," he writes, "they 

 quickly reduce the turnip to a 

 pulp. . . . Attempts to inocu- 

 late a turnip through the uninjured 

 epidermis, however, quite failed." 

 Members of the genus Rhabditis, 

 however, have no dart in the 

 mouth. The life-history of this 

 species is most remarkable, as 

 instead of males and normal 

 females, the individuals are either 

 males or protandrous hermaphro- 

 dites. 



The eelworm best known, at 

 least by repute, to cultivators is 

 Tylenchus devastatrix, Kiihn 

 (Fig. i). This species attacks a 

 great variety of plants, farm crops 

 like oats, wheat, clover and tur- 

 nips, and garden produce like 

 onions and hyacinths. In Tylen- 

 chus both sexes are slender, and 

 elongate throughout life. The 

 mouth is armed with a sharp 

 hollow dart which swells at its 

 hinder end into a trilobed knob. 

 T. devasiatrix measures only i to 

 1.5 mm. (Jj to yY inch) in length, 

 with a slender, pointed tail-region. 

 In the male there is a delicate fold 

 of skin on one or both sides of the 

 hind opening-, forming a " bursa'' 

 [bti.) ; in the female the vagina is 

 usually one-fifth of the body-length 

 in front of the tip of the tail. 

 Such details of structure as these 

 are used for discriminating be- 

 tween the various species of these 

 worms, so that careful micro- 



scopical examination is necessary in order to 

 determine them. 



These eelworms are found among the scale- 

 leaves and sheathing-leaves of bulbous plants 

 like the hyacinth and onion.* The presence of 

 the worms leads to an excessive growth of the 

 spongy tissue {parenchyma) of the plant, the 



* E. A. Ormerod, " Report 

 Injurious Insects," 1896, p. 107. 



Observations of 



* Joum. Econ. 

 PP- 91 5' Pl- viii. 



Biol., vol. iv., 1909, 



Fig. I. — Stem Eelworm {TylencJuis devastatrix, Kiihn). 

 smale: x 150. B— Male: x 150. a«.— anus ; 6k.— bursa; ^.— dart; g^.— gullet ; 

 !«/.— intestines ; ot'.— ovary ; ov</.— oviduct ; <^.— testis ; v. «'.— vas deferens; 

 z/a.— vagina ; //.—male spicules. 



iFrom " Economical Proceedings, Royal Dublin Society." Vol. I.). 



