Massee . — The ‘ Spot ' Disease of Orchids. 429 
Fig. 4. Tannin- vesicles in cells of leaf of Masdevallia Reichenbachiana ; at a the 
vesicles are small and not much vacuolated, hence take the stain readily ; at b 
the vesicles have become much vacuolated, and nearly fill the cell, hence the 
membrane is very thin and does not stain, or very slightly. The other cell- 
contents are not shown, x 450. 
Fig. 5. A cell from a diseased ‘spot’ from the leaf of Eria rosea showing 
the primordial utricle or epiplasm containing drops of tannin, stained with 
potassium bichromate ; the small angular dark patches consist of some substance 
soluble in water, and when these and the tannin drops disappear, the perforated 
epiplasm has been mistaken for the plasmodium of Plasmodiophora. x 450. 
Fig. 6. Section through portion of a ‘ spot ’ in the leaf of Bulbophyllum Carey- 
anum showing the primordial utricle presenting the appearance of the plasmodium 
of Plasmodiophora. X450. 
Fig. 7. Section through portion of a 1 spot’ in leaf of Eria rosea ; at a the 
epiplasm has contracted, become brown, and presents the appearance that has 
been mistaken for the plasmodium of Plasmodiophora ; x, the nucleus of the cell. 
At b , the epiplasm is completely covered with minute, uniform globules of tannin, 
which superficially resemble the spores of Plasmodiophora. x 450. 
