Vessels of the Onion . 
177 
EXPLANATION OF FIGURES IN PLATE XII. 
Illustrating Mr. Rendle’s paper on the Vesicular Vessels of the Onion. 
N.B. — In the case of sections mounted in corallin-soda the depth of stain of the 
callus is represented by the degree of shading. The letters D, F, refer to Zeiss’ 
objectives : 2, to his eye-piece. 
Fig. 1. Longitudinal section of the base of a young internal leaf of a spring- 
onion. a , row of young vessels ; e, epidermis. The section had been treated with 
haematoxylin, and the contents of the vessels had stained deeply. D, 2. 
Fig. 2. Tangential section of an internal succulent leaf of a spring-onion. The 
leaf had not begun to elongate. Mounted in corallin-soda to show the callus, 
which is very scanty. D, 2. 
Fig. 3. From tangential sections of the base of the outside leaf of a spring-onion 
with two green leaves and a bulb of half-an-inch maximum diameter. Mounted 
in corallin-soda. Shows the callus-formation on the transverse septa and occa- 
sionally the side walls of the vessels, a, b, D, 2 ; c, d, F, 2. 
Fig. 4. Longitudinal section of a piece of a green tubular leaf just above the 
colorless sheathing part. Mounted in corallin-soda. a , vesicular vessel ; e, epi- 
dermis with very thick and cuticularised outer walls ; chlorophyll-containing 
parenchyma; t, shows a transverse septum with a callus-stopper. Mounted in 
corallin-soda. D, 2. 
Fig. 5. From tangential sections of the base of an outside succulent leaf of a 
spring-onion treated with chlorzinc-iodine for twenty-four hours, and then, after 
thorough washing, with pi cro- Hofmann’s blue for twenty hours. Examined in 
water after again thoroughly washing. The contents of the vessels can be seen 
passing through the pits in the swollen transverse septa. F, 2. 
Fig. 6. Tangential section of an unelongated leaf of the shoot in the centre of a 
spring-onion treated for a few seconds with sulphuric acid and methyl-violet, and 
then thoroughly washed. No sign of connection between the deeply-stained 
contents of the young vessels. Shows cross-unions between two rows of vessels. 
D, 2. 
Fig. 7. Transverse septum from a young leaf of the shoot enclosed in a germinating 
onion. Mounted in corallin-soda. Shows partial staining of the wall with the 
dye, and also a little brightly staining knob to the right of this. F, 2. 
