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POPULAR SCIENCE REVIEW. 
in my own experiments, I have found that when these galls had 
attained their full size and maturity between the altered glumes 
and palece, other healthy plants, growing by the side of the 
diseased one, were only just flowering, and their germens were 
still minute and undeveloped.* 
In harmony with this method of infection of the wheat by 
TylenchiLS (^Vibrio) tritici, I have found in several grasses 
different species of these free Nematoids lying between the 
inner sheaths of the leaves near the bottom of the culm. In 
Festuca elatior I met with no less than five species in this 
situation belonging to the genera Dorylamius, Mononchus, 
and Plectus; and in the stalks of wheat and oats removed 
from stubble-fields I have frequently found specimens either of 
these genera or of Rhabditis, Aphelenchus, or Cephalobus. 
In addition to a malady of oats and maize similar to that of 
wheat, and said to be produced by the same animal, Steinbuch,f 
nearly a century ago, recognised a disease somewhat similar to 
•^purples” in two of the bent-grasses (Agrostis); and from the 
frequent presence of free Nematoids in the situation named, 
I suspect such diseases of grass would be found more frequent 
if specially looked after. As another instance of disease induced 
in plants by these animals, may be mentioned the discovery of 
KiihnJ — who has ascertained that a long-known disease of the 
common teasel {Dipsacus fullonum) is owing to the presence 
of a multitude of minute Nematoids, giving some parts of 
the flower a white filamentous appearance. These animals are 
endowed with the same tenacity of life as Tylenchus tritici, 
and for anatomical reasons evidently belong to the same genus. 
Turning nov/ from this digression concerning the remarkable 
disease in wheat which has just been described, let us consider 
the question of the tenacity of life of the individuals causing 
it, and of the free Nematoids generally. In the first place, let 
me state that the power of resisting long periods of desiccation, 
which is known to be possessed by the young of Tylenchus 
tritici, is by no means possessed by all the free Nematoids, 
although this has been more or less explicitly affirmed by several 
wTiters. As a rule, the free Nematoids are frail and delicate, 
and do not recover even after a slight desiccation of five or 
six minutes, though the case is very different with members of 
the four land and fresh-water genera Tylenchus, Plectus, Aphe- 
lenchus, and Cephcdobus : with all these there is a remarkable 
tenacity of life and power of recovery after complete desiccation. 
* For the hest means of dealing with this disease of wheat when preya- 
lent; and for other details, I must refer to M. Davaine’s admirable essay. 
t Naturforsch. xxviii. S. 233, Tab. v. 
% Zeitsch. fiir wissen Zoolog. 1857, t. ix. p, 189. 
