78 ASSOCIATION OF ORGANISMS—THE WEB OF LIFE 
In dealing with those animals that feed upon plants it is 
impossible to draw any clear line between vegetarians and para- 
sites. We shall, however, be justified in applying the latter name 
to a number of small forms which live, generally for part of their 
lives only, within the tissues of plants, one consequence being 
the formation of certain abnormal growths. Some of these will 
be dealt with later on in connection with the subject of agricul- 
J 
tural pests. The clubbing of turnip-roots (‘‘finger-and-toe” or 
Fig. 1073.—Bacteria. 1, The “‘blood portent ’ (Micrococcus prodigiosus); 2, gelatinous stage of the same. 
3, Bacteria which produce acetic acid (Bacterium aceti); 4, the same on larger scale. 5, Bacteria of Asiatic 
cholera (Spivochete cholere asiatice); 6, the same on larger scale. 7, Anthrax bacilli (Bacillus anthracis) 
with red blood-corpuscles; 8, the same on larger scale. 9, Bacteria of relapsing fever (Spivrochete Obermeieriy 
and red blood-corpuscles. 10, Symbiotic bacteria (Sarcina ventriculi) from human stomach. 4, 2, 3, 5, 7s 
and 9, X 300. 10, X 800. 4, 6, and 8, X 2000. 
“anbury ”), for example, is caused by one of the Fungus-Animals 
(Plasmodiophora brassice), which interferes with the nutrition of 
the plant, causing it to grow in an unusual way. And it not 
infrequently happens that cereals and some other cultivated forms 
are attacked by small Eel-Worms, the presence of which has a 
stunting or distorting effect. 
Most persons have noticed the curious local outgrowths known 
as “galls” that are common upon some plants, and tempt com- 
parison with the tumours and cancers of animals. They are due 
to the attacks of Gall-Flies, small forms belonging to the order 
of Membrane-winged Insects (Hymenoptera). The female gall- 
