ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 587 



invested with a mucilaginous covering which anchors it to the sub- 

 stratum ; it exercises considerable pressure on the underlying tissue, and 

 penetrates by a fine peg-like outgrowth from the part of the tube that 

 is i)ressed against the leaf surface. The piercing of the cuticle was 

 shown to be due solely to the mechanical pressure exerted by the 

 fungus. After penetration enzyme action occurs, causing the swelling 

 of the subcuticular layers. Death of the epidermal cells in advance of 

 the penetration does not occur ; there is no microscopic evidence of the 

 secretion of a toxic substance other than the cell-wall dissolving 

 enzyme. 



III. On the relation between the Infection Drop and the underlying 

 Host Tissue. — W. H. Brown * found in the course of his experiments 

 on the same fungus that the germ tubes were unable chemically to 

 affect the cuticle of the host, nor do they secrete any toxic substance 

 which can pass through the cuticle and bring about the death of the 

 underlying cells. The fungus is unable to affect the underlying tissue 

 until the obstacle afforded by the cuticle has been overcome. Chemical 

 action being excluded, penetration of the cuticle must take place in a 

 purely mechanical way, as was demonstrated by Blackman and Welsford. 



Another paper by W. Brown f on the same subject gives a resume 

 of the subject, with special reference to the behaviour of Botrytis cinerea. 

 An extract of the fungus was made and injected into the living 

 plant, with the result that the cell-walls were disorganized and the cells 

 killed. In half-an-hour after treatment the cells of a potato fell apart 

 owing to the process of disorganization — the death of the cell is shown 

 by the brown or black coloration of the contents. The action exactly 

 resembled that of the parasite. Brown also found that the extract had 

 no effect when applied to the surface of the plant ; it is unable to 

 penetrate the outer cuticle. Notes are also given as to the behaviour 

 of tl^e extract to reagents — acids, alkalies, salts, etc. 



Potato-wilt and Tuber-rot caused by Fusarium euinartii.| — 



E. J. Haskell states that in only two cases of Fusarium attack — 



F. oxysporum and F. trichothecioides — is the wilting of the foliage due to 

 the fungus Fusarium. He has proved that F. eumartii also gives rise 

 to both symptoms of disease. The culture experiments were made 

 originally from Fusarium spores produced on rotting potato tubers. The 

 stems inoculated became diseased, and the leaves wilted. The stems 

 below ground were also attacked, and the tubers. From these latter the 

 fungus was again isolated, and proved to be identical with the original 

 strain. 



Spore Variation in Neopeckia Coulteri.§ — J. S. Boyce calls atten- 

 tion to the occurrence of variations in the number of septa in this fungus, 

 a parasite of several species of Pines in America. Normally the spores 

 are uniseptate and dark brown, while those of Herpotrichia are thrce- 



* Ann. Bot., xxx. (1916) pp. 399-406. 

 + Journ. Board Agric, xxiii. (1916) pp. 474-8. 

 % Phytopathology, vi. (1916) pp. 321-7 (3 figs.). 

 § Phytopathology, vi. (1916) pp. 357-9. 



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