2O4 N. H. COWDRY. 



PLATE II. 



FIG. 7. A plantlet of the marrowfat variety was heated to a temperature of 

 from 65 to 73 degrees C. for 40 minutes. A cell from a radicle 10 mm. long 

 is figured. A few mitochondria! granules still persist with others not so 

 strongly stained and almost indistinguishable in the granular or mealy proto- 

 plasm. The black granules at the periphery of the nucleus have lost their 

 stain. 



FIG. 8. The plantlet was exposed to a temperature of about 10 degrees C., 

 in an ice box, for 4 days. The cell figured is from a radicle 9 mm. long and 

 shows filaments, not strongly stained, clustering about the nucleus and remain- 

 ing unchanged, although some show strongly stained nodes. The vacuoles in 

 other cells contain intensely stained and enlarging mitochondrial spheres and 

 shreds of protoplasm. 



FIG. 9. Showing effect of prolonged exposure to a temperature of about 

 10 degrees C., in an ice box, for 18 days. The cell figured is from a radicle 

 6 mm. long. The filaments have, in most cases, segmented into intensely 

 stained granules and short rods. Those in the vicinity of the nucleus are en- 

 larged. The protoplasm is distinctly reticulate. 



FIG. 10. Exposed to the low temperature of a freezing mixture of ice and 

 salt and gradually restored to room temperature. The cell from a radicle 5 

 mm. long, shows rather minute granular mitochondria of varying intensity of 

 stain. The protoplasm is distinctly alveolate. No mitochondrial granules 

 occur in the alveoli. 



FIG. ii. The plantlet was submerged in water for 24 hours. In the cell 

 figured from the inner cortex of a radicle 9 mm. long, are many enlarged 

 granules and a few short rods varying in intensity of stain and evenly dis- 

 tributed in the protoplasm. There are no filaments in this cell, but in cells of 

 the outer cortex are many lightly stained filaments which are segmenting into 

 shorter rods. The vacuoles contain many intensely stained mitochondrial 

 spheres. 



FIG. 12. The plantlet was enclosed in an air-tight space of about 15 c.c. for 

 one day. A cell from the middle cortical layers of a radicle 5 mm. long was 

 selected. The mitochondrial filaments have assumed the form of short rods, 

 spheres and rings which show no tendency to approach the nucleus. They lose 

 their stain entirely in the outermost cells. The vacuoles are large and contain 

 few and sometimes no enlarged mitochondria. 



