No. 5.] 



PEA AND XASTURl'U'.\r SEEDS. 



2I 7 



"' 



FIG. 3. 



DESCRIPTION OF FIGURES. 



/../". = bast fibers. tr. = tracheid. 



ph. = phloem. jrj'. = xylem. 



( - = center of stem. 



FIG. i. Part of a cross-section of the stem of a normal 



pea seedling. 

 FIG. 2. Part of a cross-section of the stem of a dwarf 



pea seedling. 

 FIG. 3. Cross-section of a sector of the stem of a normal 



nasturtium seedling. 

 FIG. 4. Part of a cross-section of the stem of a dwarf 



nasturtium seedling. 



I-' it,. 4. 



have been given and discussed were all drawn from three 

 plants of each species, nevertheless that the general results 

 are trustworthy is shown by another set of observations made 

 on different pea plants. These gave the following results : 

 Ratio of diameters of dwarf and normal plants, 111:62 (.56); 

 cells in a given sector (7), 165 in normal and 106 in dwarf 

 (.64); cells in strips from center to circumference proportional 

 in width to the size of the cross-section, 219 and 144 respec- 

 tively (.66). The number of cells in a definite area was 29 in 

 the normal and 44 in the dwarf. These measurements con- 

 firm those already discussed, for they show that the normal 

 stem is larger in cross-section, is composed of a greater 

 number of cells, and of larger cells than the dwarf. 



The next question to be examined is the degree of differen- 

 tiation of the various plants. This differentiation may be 

 studied in the fibre-vascular bundles, where we may note the 



