. 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. 31 Somewhat doubtful cases are the outgrowths resembling aerial roots which arise on Laurus canariensis attacked by Eocdbasidium lauri. Geyler, their discoverer, regarded them as deformed stem- shoots, but they resemble rather the galls of the alpine-rose. § 6. EFFECT OF PARASITIC FUNGI ON CELL-CONTENTS. The most common and, at the same time, most apparent effect
. 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. 31 Somewhat doubtful cases are the outgrowths resembling aerial roots which arise on Laurus canariensis attacked by Eocdbasidium lauri. Geyler, their discoverer, regarded them as deformed stem- shoots, but they resemble rather the galls of the alpine-rose. § 6. EFFECT OF PARASITIC FUNGI ON CELL-CONTENTS. The most common and, at the same time, most apparent effect of parasitic fungi in this direction, is the stimulation to cell-division and cell-multiplication. This occurs chiefly in young tissues, or in those still in process of growth, and gives rise to numerous peculiar outgrowths and swellings, some of which have already been referred to. The parenchyma of mature tissues may also exhibit secondary cell-division, when under the influence of a parasitic fungus. This I found to be the case in leaf- petioles of Umbelliferae attacked by Protomyces macrosporus (Fig. 9). The epidermis and vascular bundles are never disturbed, but the intervening tissues are permeated by an intercellular mycelium, which causes the cells to divide into a large number of delicate-walled chambers, ° 111 ^**^- ^-—Secondary cell-division all contammg nuclei smaller than those in parenchyma of petiole of ^cyo- . ,. ^ ^ ,, —^ ;pQdium as a result of Protomyces of neighbouring undivided cells. The macrosporus. The nuclei of the . , new cells are much smaller than same thing is observed m plants of those of the primary ceU. (Com- ° . ^ pare Fig. 47.) (v. Tubeuf del.) Viola odorata inhabited by Urocystis violae; the mature parenchymatous cells become divided up by means of delicate walls running in various directions into numerous chambers or secondary cells, which Wakker in describing has named " nutritive ; ^ This new tissue remains permanentl
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