202 N. H. COWDRY. 



PLATE I. 



FIG. i. Normal cells of the cortex near the meristem of a radicle about 10 

 mm. long. The mitochondria are filamentous and granular, and exhibit a 

 varying intensity of staining reaction. They show little tendency to cluster 

 around the nucleus or to enlarge. The vacuoles contain mitochondrial granules. 



FIG. 2. Showing the effect of centrifuging for one hour. The radicle is 

 about 6 mm. long and has not yet elongated. Mitochondria are few and un- 

 affected in position in the protoplasm and in the vacuoles they are evenly dis- 

 tributed among protoplasmic shreds. The heavy nucleus adjoins the cell wall 

 while the greater part of the protoplasm lies between the nucleus and the 

 vacuole. The continuity of the protoplasmic lining of the cell wall is unbroken. 



FIG. 3. Plasmolysis caused by immersion of the radicle, about 7 mm. long, 

 in a 20 per cent, solution of cane sugar, for two days. Mitochondria are few 

 in number and have enlarged into spherules with centers lightly stained. The 

 protoplasm is very unevenly stained and contains no vacuoles. Intensely 

 stained masses appear at the periphery of the nucleus. 



FIG. 4. Illustrating the effect of drying the plantlet for 36 hours. Cell 

 from a radicle about 9 mm. long. The mitochondria, differing in size and 

 intensity of coloration, are granular and show no inclination to approach the 

 nucleus. The nucleolus is only faintly stained. Other cells show a large 

 vacuole with globules of protoplasm and many mitochondrial spheres. 



FIG. 5. The plantlet was heated to a temperature of from 43 to 46 degrees 

 C. for three hours. The radicle is short, being only 5 mm. long. Mitochon- 

 drial granules are very numerous and lightly stained. The plast-like forms are 

 characteristic of the Alaska, a green variety of pea. The protoplasm is uni- 

 form but, where thin, it becomes alveolate. 



FIG. 6. Plantlet exposed to a temperature of from 47 to 49 degrees C. for 

 30 minutes. Cells from a radicle 9 mm. long. Mitochondria are few and 

 granular with increased intensity to stain. The strongly stained masses at the 

 periphery of the nucleus probably result from the increased temperature. 



