EEL- IV OR MS OX LEAVES OF CULTIVATED TLA NTS. 



411 



considerably, as also pelargoniums, salvias, cinerarias, 

 begonias, cyclamen, and Easter lily. 



These leaves are quite naturally divided into two 

 groups as regards their external appearance. In the 

 coleus, cineraria, and salvia, for example, the foliage, 

 while retaining its natural shape, becomes blotched with 

 angular patches which at first turn yellowish green and 

 then brown. The appearance of a blotched salvia leaf 

 is shown at a in the engraving. In such leaves theveinsare 

 prominent and the surrounding pulp or green part is not 

 particularly abundant, so that the veins form a barrier to 

 the unimpeded progress of the worms. A microscopic 



are wet, even slimy in appearance, and the cause of the 

 decay is easily communicated to a healthy leaf by placing 

 a diseased specimen upon it. In the case of the coleus, 

 upon the other hand, the foliage is dry. In some in- 

 stances the worms may be seen upon the free surface of 

 the leaf, and in the first group in particular, the spread of 

 the decay throughout the leaf may, in larger part, result 

 from the migration of the worms upon the surface and 

 their entrance through the stomata into new healthy 

 areas. 



A form somewhat midway between the two types is 

 that seen in the bouvardia and[sho\vn at < in the engrav 



Eel-Worms and their Work. 



examination of the blotches shows that the well-defined, 

 irregular lines between the healthy and diseased parts 

 are made by the comparatively dense substance of the 

 veins. 



The second group of leaves is composed of those like 

 the chrysanthemum, geranium and begonia, in which the 

 pulp is abundant, the leaves being comparatively thick 

 and the venation not so prominently netted as in the coleus 

 and salvia. Therefore, as a rule there is no distinct 

 blotching of the leaf, but instead the decaying spot spreads 

 indefinitely until the whole is involved and the leaf falls 

 away. At /' the appearance of a geranium is illustrated 

 as partially destroyed by the nematodes. Such leaves 



ing. In this, the outline is not so much due to the veins 

 as the sharp contrast of color between the green, healthy 

 parts and the light brown of the affected portions. 



The microscopic appearance of the foliage nematodes 

 is shown at d and one of the worms as seen in the leaf 

 substances is represented at f. They vary much in size 

 according to age, but in general are about j^fu of an 

 inch long, tapering but little to the blunt head end, and 

 gradually in the opposite direction to a slender, ofte-n 

 sharp pointed tail. 



It is not our purpose to enter into a full consideration 

 of the life history of the eel-worm, but suffice it for the 

 present purpose to say that there are the two sexes which 



