214 DIMON. [VOL. II. 



A. What is the relative size of the cross-section of a normal 

 and of a dwarf plant ? 



/>'. What is the relation between the number of cells in a 

 normal cross-section and a dwarf one ? 



C. What is the relation between a normal and a dwarf 

 plant, as regards the size of the cells ? 



D. How does the degree of differentiation of the normal 

 compare with that of the dwarf plant ? 



Attempts were made to compare sections of the dwarf 

 seedling under the microscope with sections of a normal seed- 

 ling of the same size, as a check, as well as with the nor- 

 mal seedling of the same age, but the only specimens of check 

 seedling available for comparison were so much larger than 

 the dwarf that allowance must in every case be made for a 

 discrepancy. The cross-sections studied were all cut free- 

 hand from a level less than an inch from the ground in the 

 growing plant. 



The first question in the preceding paragraph relates to the 

 relative size of the cross-section of the stem of the normal 

 and dwarf plants. In the cross-sections represented by the 

 figures the diameters of the peas have the relative values of 

 36 and 53, or the diameter of the dwarf pea is .68 as great as 

 the diameter of the normal ; the diameters of the nasturtiums 

 have the relative values of 30 and 38, or the diameter of the 

 dwarf is .79 as great as that of the normal. Cross-sections of 

 the stem of the check plants have the values 46 and 33 for 

 the diameters of the pea and nasturtium, respectively. The 

 dwarf and normal plants were five weeks old and the check 

 plant two and one-half weeks old. The plants selected for 

 examination were typical ones, and the fact that the ratio 

 between the diameters does not correspond to the average 

 ratios between the heights given in Table II may be explained 

 in two ways : 



i. The ratio between the heights, as was seen, decreases 

 with the increasing development of the plants, and the 

 degree of development of the plants from which the cross- 

 sections were taken was probably not the same as that of the 

 plants measured in Table II. 



