26 REACTION OF HOST TO PARASITIC ATTACK. 



be described when we consider JEuphorbia with Aeeidium 

 euphorhiae (Fig. 6), house-leek with Endophyllum, anemone with 

 Aeeidium (Fig. 190), and cowberry with Calyptospora (Fig. 202). 

 Where plants, like the cowberry and anemone, live in com- 

 munities, then these elongated individuals rise above their 

 healthy neighbours, and the fructifying fungus has a better 

 chance of having its spores distributed by wind. It must, 

 however, be observed that when hypertrophy of a whole shoot 

 or plant occurs, every part need not be enlarged to a propor- 

 tionate extent ; in fact some parts generally remain abnormally 

 small, e.g. leaves in cases of rusts upon cowberry, fir, anemone, 

 and others. On the other hand, both shoots and leaves may 

 be abnormally enlarged, as in cases of alder with Exoascus 

 Tosquinetii or Ex. epiphyllus.^ 



Hypertrophy of the roots occurs on alder, where large tubers 

 are produced by Frankia (Fig. 21). On Leguminosae, tubercles 

 of various sizes are caused by Bhizobium (Fig. 22). Eoots 

 of Juncus develop thick-lobed outgrowths as a result of Schinzia 

 (Fig. 179). Eoots of turnip infested by Plasmodiophora have 

 irregular swellings of all sizes (Fig. 315). Mycorhiza frequently 

 exhibit tubercles or balls formed by the massing together of 

 very short dichotomously branched rootlets into clumps (Fig. 18). 

 Cycad-roots, under the influence of Ehizohium and Nostoc, also 

 exhibit hypertrophy.^ 



We shall now proceed to consider hypertrophy of the repro- 

 ductive organs, and at the same time to notice some other 

 changes induced in the flower by parasitic fungi. 



Influence of parasitic fungi on the development of reproductive organs 



of host-plant. 



Disease of the flower and fruit, when not caused by fungi 

 which kill the cell, generally causes striking floral malformation. 

 These we may group as follows : 



1. Atrophy or total suppression of flowers. 



2. Arrested development of flowers. 



3. Development of rudimentary organs. 



4. Abnormal formation of flowers. 



5. Hypertrophy of parts. 



6. Transformation into sclerotia. 



^ See also § 7. ° Schneider, Botanical Gazette, 1894, p. 25. 



