THE MICROSCOPE. 147 



a time after it appears above ground it is pure white. In this stage 

 of development nothing but starch-forming-corpuscles are found. 

 The continued growth of the young bulb presently causes it to burst 

 its enswathing leaf petioles which gradually wither and drop off, the 

 bulb changing to a bright green, and the starch-grains disappear from 

 the cortical portion of the bulb and chlorophyll-grains take their place. 

 A similar phenomenon is seen in the leaves of Iris floi-entiim, which 

 are white when first put forth and contain starch-forming-corpuscles, 

 but as they unfold, rapidly become green by the replacement of the 

 starch-grains by chlorophyll. The same change occurs when a 

 potato tuber is accidentally exposed to light, the portion above 

 ground becoming green by the development of chlorophyll at the ex- 

 pense of starch. In the closing paragraph of his paper, Mr. 

 Shimper mentions an interesting point which has been brought to 

 light in the course of the original investigation. "There is no such 

 great difference between assimilating (chlorophyll-corpuscles), 

 and non-assimilating cells (starch forming-corpuscles), as was 

 thought to exist. In a cell which contains no chlorophyll there are 

 certain organs which produce starch, and these organs are nothing 

 more than imperfectly developed chlorophyll-corpuscles, which may 

 develop into perfect chlorophyll-corpuscles, under the influence of 

 light. On the other hand, chlorophyll-corpuscles are not always 

 merely assimilatory organs, they perform in the conducting tissues 

 and in the reservoirs of material the same functions as the starch- 

 forming-corpuscles in cells which do not assimilate; that is, they pro- 

 duce starch from assimilated substances which are conveyed to them 

 from other parts of the plant." 



These investigations of course give little clue as to how the 

 chemical elements of starch are combined in the plant cells, but 

 they show that there are undoubtedly various intermediate sub- 

 stances formed between the crude elements that are taken up by the 

 roots, and leaves. In investigating this subject comparatively high 

 powers are required, 800 to 1000 diameters are desirable, although, 

 a first class \ in. objective with a i inch eye-piece will do very well 

 for many specimens. Recently formed portions of tissue should be 

 chosen for examination, and if not available for immediate use the 

 specimens may be preserved in proof alcohol. 



Detroit, Oct. 1881. 



