PRINGSHEIM S KKSEARCUES ON CHLOROPHYLL. 101 



shaped bodies, behave when decolorised by insolation in tVie 

 same way as the chlorophyll-corpuscles in Nitella. The light- 

 killed bands stiffen while retaining their normal form and 

 configuration (fig. 19). The ground-substance of chloro- 

 phyll-corpuscles and masses appears thus under the influ- 

 ence of light to have lost its [)0wer of swelling in water and 

 watery solutions, and in this, as in the retention of its form 

 and shape, we have a marked difference between the de- 

 structive effects of light and of heat. 



Before studying the effe'ct of light on the bodies contained 

 in the chlorophyll-corpuscles, it is necessary to consider what 

 these substances are and how they are distributed. 



From the time when Mohl first demonstrated the common 

 association of starch with chlorophyll, and subsequently Bohm, 

 by his improved iodine test, afforded means of more easily 

 determining its presence in chlorophyll-corpuscles, starch has 

 been regarded as a necessary construction product of chloro- 

 phyll-corpuscles. Mohl,^ indeed, failed to discover it in many 

 plants, and Bohm,~ although he found it in many cases where 

 Mohl had a negative result, yet mentions certain plants as 

 l)ossessing no starch, e.g. Alliu?n Jistulosmn, Asphodelus 

 luteus, Orchis militaris, Lactuca sativa. Some years later 

 colourless bodies not consisting of starch were observed in 

 chlorophyll-corpuscles, and these have usually been regarded 

 as fat-globules or oil-drops. Thus Pringsheim,^ in 1855, 

 showed that in Vancheria sessilis there is no starch, but that 

 small oil-globules occur which supply the formative material 

 for the oogonia. Nilgeli* afterwards pointed out their existence 

 along with or instead of starch in the chlorophyll-corpuscles 

 oi lihipsalisfu7ialis, Cereus va7'iabilis , aud in non-green fresh- 

 water and marine Alga. Then Sachs^ showed that there is no 

 starch in Allium ccpa; and finally, Briosi^ noticed that starch 

 is wanting in the chlorophyll-corpuscles of Musaccce, but that 



' " Untersuchungen iiher die anatoniisclien Verhaltnisse des Chloro- 

 phylls," Dissertation vom Jalire, 1837 (' Verm. Schrift,' xxvi) ; and "Ueber 

 deu Bau des Chloropiiyll^," 'But. Zeit.,' 1855. lu his paper of 1837 

 Mohl recognised tliat tiie starch content of chlorphyli-corpuscles was a 

 reserve nialerial for the plant. 



^ " Beilrage ziir Kenntuiss des Chlorophylls," ' Sitzungsber. d. Wien. 

 Akad.,' October, 1856. 



3 'Monatsber. d. Berl, Akad. d. Wiss.,' March, 1855. 



* ' Die Starkekorner,' p. 398 ; ' Pflauzeuphysiologische Uutersucliungeu,' 

 Pt. 2, 1858. 



* 'Bot. Zeit.,' 1862, p. 369; 'Flora,' 1863; 'Experimental Physio- 

 logie,' p. 28. 



* 'Bot. Zeit.,' 1873, p. 529. Briosi's results, as Vines points out in 

 'Nature,' xxiii, p. 562, have been shown to be incorrect by HoUe and 

 Godlewski in 'flora,' 1877. 



