196 



NATURAL SCIENCE. 



March, 



worm. Not only does the English observer note the occurrence of 

 nematodes in root-excrescences for the first time, but gives two 

 figures in his paper, here reprinted by kind permission of the editor 

 of the Gardeners' Chronicle. One of them is an enlarged view of what 

 is now recognised as a female of Heterodera radicicola embedded in 

 the hypertrophied tissue of the root. Eggs and young larvae are 

 figured, and Berkeley mentions that these occur in free cyst-like 

 bodies, which appear to be regular membranous sacs. 



" The cyst," he says, " was destitute of any evident organic 

 structure, was not affected by iodine and sulphuric acid, but showed 

 some appearance of giving way under caustic potash. It was clear, 

 then, that it did not consist of cellulose, but might possibly be some 



Fig. 2. — "Cyst" female Heterodera from root-galls of Fig. 1, with eggs and young 



larvae. 

 From the Rev. M. J. Berkeley's paper in Gardeners' Chronicle, April 7, 1855. 



modification of xylogen. It is not conceivable that such a cyst could 

 have been deposited by the vibrio itself, and we must therefore con- 

 sider it as due to the irritation caused by the presence of the eggs, 

 and exactly analogous to the cysts produced by the larvae of the 

 cestoid worms in animal structures. We are not aware that anything 

 of the kind has ever been observed before in vegetable parasites ; for, 

 though the tissues of vegetables are greatly altered by the presence 

 of the larvae, which produce galls, it does not appear that they ever give 

 rise to a free cyst, as in the present case, differing altogether from the 

 surrounding tissues." 



It is obvious that although Berkeley looked upon the body of the 

 female as a cyst, his careful attempts to ascertain its nature by 

 chemical means placed him within measurable distance of clearing 



