E. M. Dotdge 45 



Plate V. Mangoes in a more advanced stage of the disease; deep longitudinal cracks 

 have formed. 



Plate VI. In this case the whole inflorescence has been destroyed ; the one remaining 

 fruit fell off as the photograph was taken. 



Plate VII. Photomicrograph of section through fruit, showing an early stage of the 

 disease. The dark area consists of crushed, discoloured cells, with masses of bacilli in 

 the intercellular spaces. (Photographed with Zeiss' achromatic objective D, and 

 compensating ocular No. 6.) 



Plate VIII. Photomicrograph of section through fruit in a more advanced stage of the 

 disease. The superficial cells are crushed and dead ; there are very few bacilli in 

 this region. They are very numerous in the more deeply seated tissues, a small 

 fibro-vascular bundle at the foot of the plate is surrounded by them, but untouched. 

 Same magnification as Plate VII. 



Plate IX. Detail from Plate VIII. , in the neighbourhood of the fibro-vascular bundle. 

 The bacilli can be clearly seen in the intercellular spaces, wedging the cells apart. 

 (Zeiss oil imm. ; obj. 2 mm., 1-4 app. ; comp. ocular No. 6.) 



Plate X. Photomicrograph of section through diseased spot on leaf. The increase of 

 thickness due to the swelling of the disorganised cells is very evident; two small 

 vascular bundles in the field have not been attacked. The organism has invaded 

 the tissues from the underside of the leaf, the palisade cells still being intact. There 

 are no stomata in the epidermis of the upper side of the leaf. (Same magnification 

 as Plate VII.) 



Plate XI. (a) Plate culture of Bacillus mangiferae photographed after five days at 25° C. 



(b) Crystals from plate culture in + 15 nutrient agar, 10 days old. Photographed 

 from a drawing made with camera lucida, and Zeiss achrom. obj. AA., ocular No. 1. 



(c) Stab cultures in nutrient gelatine photographed after 20 days at 20° C. 

 {d) The same culture seven days later. 



Plate XII. a — o. Development of a small colony as observed on agar hanging block. 



For fuller explanation see text. (Zeiss 1/12 obj. oil imm. and No. 12 compensating 



ocular.) 

 Plate XIII. a — h. Stages in the segmentation of long threads developed in nutrient 



broth containing 8-5 NaCl. Full explanation in text. 

 Plate XIV. (a) Photomicrograph of chains formed in pellicle on nutrient broth, eight 



days at 30° C, stained with MacConkey's capsule stain. 



(b) From same preparation as above, drawn with camera lucida, Zeiss oil imm. 

 obj. 1/12 and compensating ocular No. 12. 



(c) Bacilli from 2% dextrose broth, three days at 30° C. (Paraboloid condenser, 

 Zeiss apochrom. obj. 3 mm., apert. 0-95, compensating ocular No. 18.) 



(d) Capsuled rods from ring above nutrient broth, 15 days at 30° C, MacConkey's 

 capsule stain. Zeiss oil imm. obj. 1/12, comp. ocular No. 12. 



(e) Bacillus mangiferae with flagella, from culture on nutrient agar, 20 hours at 

 25° C. Stained by Ellis' modification of Loeffler's method. Same magnification as (d). 



[Note by Editor. It has been necessary to reduce the size of some of the figures; 

 for which allowance must be made in the estimate of magnification. 



Plates VII, VIII, IX and X have each been reduced by one-eighth. 

 On Plate XI, figs, c and d have been reduced by one-eighth. 

 Plate XIII, all figures reduced by one-sixth. 

 Plate XIV, figs, c and e reduced by one-fifth.] 



Botanical Laboratories of the Union of South Africa, Pretoria. 



