No. 5.] PEA AND NASTURT1LM SEEDS. 215 



2. The stem of small plants is always thicker in proportion 

 to the size of the plant than that of large plants, so less 

 difference in cross-section than in height is to be expected. 

 Interpret this discrepancy as we may, the fact remains that 

 the stem of a normal plant has a greater diameter than the 

 stem of a plant sprung from a seed part of whose cotyledons 

 has been cut off. 



The ratio between the number of cells in a normal cross- 

 section and a dwarf cross-section can be determined by count- 

 ing the number in a definite sector of each. The results of 

 counting the number of cells in a sector of 30 are : in the 

 normal pea (Fig. i), 410 cells ; in the dwarf pea (Fig. 2), 311 

 cells ; in the normal nasturtium (Fig. 3), 223 cells ; in the 

 dwarf nasturtium (Fig. 4), 208 cells ; in the check pea, 404 

 cells; in the check nasturtium, 219 cells. The dwarf plant 

 has, therefore, decidedly fewer cells than the normal ; in the 

 case of the pea .76 as many, and in the case of the nasturtium 

 .93 as many. If the ratio between the number of cells was 

 the same as the ratio between the diameters of the cross-sec- 

 tions, it would mean that the cells must be of the same size ; 

 since the former ratio is larger for both pea and nasturtium, it 

 means that the cells of the normal are larger than those of the 

 dwarf plant. 



The conclusion as to the size of cells in dwarf and normal 

 plants may be confirmed directly by counting the number of 

 cells in a definite area. Proceeding to do this for Parenchyma 

 cells, the following results were obtained: In the normal pea 

 (Fig. i), 22 cells ; in the dwarf pea (Fig. 2), 43 cells ; in the 

 normal nasturtium (Fig. 3), 21 cells ; in the dwarf nasturtium 

 (Fig. 4), 32 cells ; in the check pea, 50 cells ; in the check 

 nasturtium, 29 cells. The regions counted were all in the 

 same part of the stem, and other counts were made that cor- 

 roborate the figures here given. These figures confirm the 

 conclusion reached in the preceding paragraph as to the size 

 of the cells in normal and dwarf plants ; but in the case of the 

 check pea plant it is found that the cells are smaller than those 

 of the dwarf plant. 



Though the statistics from microscopic examination that 



