482 SUMMARY OF CURRENT RESEARCHES RELATING TO 



them, is described in detail in the jjaper in a number of different 

 plants. They can be classified under the following heads : — 



A. — Starch-producers spherical. 



a. They are formed only in the protoplasm which surrounds 



the nucleus. 



a. They produce starch-grains in their entire mass 

 (Cohcasia). 



y6. They produce starch-grains only in their peri- 

 pheral portion {PMlodendron, Amomum). 



b. They are formed in the protoplasm which surrounds the 



nucleus, and sparingly also in the rest. 



a. They produce starch-grains in their entire mass 

 (Beta trigyna). 



c. They are formed in the whole of the parietal protoplasm, 



and not specially in the region of the nucleus. 



a. They produce starch-gi'ains in their entire mass 

 (Melandryum). 

 B, — Starch-producers fusiform. 



a. They are formed ouly in the protoplasm which surrounds 

 the nucleus. 



yS, They produce starch-grains only in their peri- 

 pheral portion (Phajiis). 

 c. They are formed in the entire parietal protoplasm, and 

 not specially in the region of the nucleus. 



a. They produce starch-grains in their entire mass 

 (^Melandri/um), 

 C — Starch-producers at first spherical, afterwards elongated. 



a. They are formed only in the protoplasm which surrounds 

 the nucleus. 



B. They produce starch-grains only in their peri- 

 plaeral portion {Canna gigantea). 



A comparison of these starch-producers with chlorophyll-grains 

 reveals a very strong similarity between them. They appear to be 

 identical with the leucophyll-grains, especially those in the deeper 

 cells of etiolated stems, where they are perfectly colourless and very 

 evanescent. The mode of formation of the three structui-es is very 

 similar. Further than this, starch-producers can, under the influence 

 of light, be transformed into chlorophyll-grains. This transformation 

 may take place normally in the course of development of an organ 

 which has, when young, been excluded from the light by being buried 

 in the soil or concealed beneath a thick covering of leaves, and then 

 exposed to light, as the leaves of Iris, tubers of Plmjus grandifolius, 

 &c. Parts abnormally exposed to light, as potato-tubers, form in the 

 same way false chlorophyll-grains from their starch-producers. It is 

 not, however, all starch-producers that are capable of being thus 

 converted into chlorophyll-grains. It may, in fact, be assumed as a 

 general law that leucophyll-grains, etiolin- grains, and starch-producers 

 are nothing else than the young colourless condition of chlorophyll- 

 grains. 



