CEdema of the Tomato. 127 



DESCRIPTION OF PLATES. 



Plate I. Photograplis showing fedematous cushions on stem and 

 leaves of tomato. 



Plate II. Photograph showing detail of connection of tomato cut- 

 tings with the hydrant, and drops of water hanging from edges of 

 leaves which were forced through the veins by the water pressure. 



Plate III. Anatomical structure of fjedematous cushion on leaf 

 vein. Figure 4, healthy part of vein; figure 5, from center of cushion. 



Plate IV. Anatomical structure of cedematous cushion in mesophyll 

 of leaf, near termination of leaf vein . Figure 6, appearance of pmall 

 cushion magnified with pocket lens. Figure 7, section through edge 

 of small mesophyll cushion. Figure 8, section through center of 

 partially collapsed mesophyll cushion. Plate IV was made from 

 specimens sent by L. R. Jones, of Burlington, Vermont. 



Plate V. Structure of young cedematous cushion in young stem of 

 No. 18 variety, showing also detail of tissue. In this and all the 

 plates which follow, nied. = ])ort[on of parenchyma from the pith of 

 medulla; to = woody cells; c« = cambium zone; 6 = bast; c p.= 

 cortical parenchyma ; co\= collenchyma ; ch = chlorophyll layer of 

 cells ; ep = epidermis 



Plate VI. Figure 11, from center of young cedematous cushion in 

 young stem of No. IS variety, taken from same series as figures 9 and 

 10 of Plate V. Figure 12, from center of older cushion on older part 

 of stem of No . 1 8 variety. 



Plate VII. Comparative study of oedamatous cushions produced 

 artificially, with the normal tissue on opposite side of stem. Figures 

 13 and 14, from No. 18 variety; figures 15 and 16, from Lorillard 

 variety. 



Plate VIII. Comparative study of tissue firmness of No. 18 variety 

 (figure 17) with Lorillard variety (figure 18) at same stage of growth. 



SUMMARY FOR PRACTICAL PURPOSES. 



The oedema of the tomato is a swelling of certain parts of the plant 

 brought about by an excess of water which stretches the cell walls, 

 making them very thin and the cells very large. The excess of water 

 may be so great that the cell walls break down, and that part of the 

 plant dying, exerts an injurious influence in adjacent parts. 



The excess of water in the tissues is favored by the following 

 conditions : 



