. Diseases of plants induced by cryptogamic parasites; introduction to the study of pathogenic Fungi, slime-Fungi, bacteria, & Algae. Plant diseases; Parasitic plants; Fungi. EFFECT OF PARASITIC FUNGI ON THE FORM OF HOST-PLANT. 25. the ovules become atrophied, whereas the rest of the flower is hypertrophied. Similarly witli fiowers of cowberry deformed Ijy Exohasidiain. 2. Hypertrophy.—Alany para- sitic fungi cause abnormal enlarge- ment or other malformation of plants which they attack. The simplest case of hypertrophy is seen in the enlargement of a uni- cellular plant as a result of an
. Diseases of plants induced by cryptogamic parasites; introduction to the study of pathogenic Fungi, slime-Fungi, bacteria, & Algae. Plant diseases; Parasitic plants; Fungi. EFFECT OF PARASITIC FUNGI ON THE FORM OF HOST-PLANT. 25. the ovules become atrophied, whereas the rest of the flower is hypertrophied. Similarly witli fiowers of cowberry deformed Ijy Exohasidiain. 2. Hypertrophy.—Alany para- sitic fungi cause abnormal enlarge- ment or other malformation of plants which they attack. The simplest case of hypertrophy is seen in the enlargement of a uni- cellular plant as a result of an endophytic parasite, ejj. Pi/oho/i/s Kh'inii with Plcufmclirhis. The same example is also the simplest possible case of a gall caused by a plant, and distin- guished by the name of " fungus- galls " or Mycocecidia, from Zooce- cidia, the galls caused Ijy animals. Larger galls occnir on leaves attacked by Synchjjtriiim, where not only the single cell attacked becomes enlarged, but also the surrounding cells; these galls, however, form but tiny points on diseased leaves. Similar small and local enlargements of the leaf-cells, accompanied frequently by cell multiplication, are caused by many other fungi, ejf. species of Exoascm. More extensive malformation may embrace some part or even the whole leaf, so that it is more or less enlarged and beset with blister-like outgrowths, as with other Exoasceae (see Figs. 62 and 64). Other gall-forms are presented by ExohasicUum on the alpine-rose (Fig. 259), where the gall is always localized to a small area of the leaf, and on the cowberry, where the gall may extend over whole leaves, and even include the shoot (Fig. 256). Hypertrophy of the whole shoot, resulting in elongation and thickening of the twigs, is a phenomenon frequently met with in the " witches' brooms," to be referred to later. And just as entire branch-systems may become hypertrophied and elon- gated, so may whole plants, if the mycelium, instead of rem
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