Missed Colouring Matters ivith the Spectrum Microscope. 131 



leaves of many terrestrial plants in autumn.* The chlorophyll has 

 disappeared, and perhaps more xanthophyll has been formed. How- 

 ever, confining our attention to the colouring matters sohible in 

 •water, it will be seen that the band X is visible, but that instead of 

 being isolated as in the spectrum of Palmella cruenta, there is a 

 broad absorption-band Y extending fi-om it some distance towards 

 the blue end, and also another well-marked band Z, between the 

 green and the blue. 



3. The purple Floridea is a similar plant to the red, only in 

 an unchanged condition. The spectrum shows a band W in the 

 red, due to a blue colouring matter, which along with the chloro- 

 phyll causes the plant to be of a peculiar duU purple colour, and 

 not red, as in the former example. It will be seen that the band Z 

 is the same as in the red specimen, but that Y is relatively so much 

 darker that the narrow band X is almost enthely obscured, and yet 

 that it does really occur is proved by the bright green-yeUow band 

 in the spectrum of the fluorescent hght of the colouring matter 

 dissolved out by water. 



4. The spectrum of OsciJkdoriw is seen to the greatest advan- 

 tage by examining a mass of the healthy hving fronds which creep 

 up the sides of a bottle containing the impure natural material. 

 They are then free from Biaiomacece and particles of mud, and by 

 collecting them together on a piece of thin glass with a httle water, 

 so that there are no vacant spaces to signify, concentrated sunhght 

 penetrates through them, and gives a spectrum with the two weU- 

 marked absorption-bands, shown in the figure, as described by Kay 

 Lankester.t "^^^en the plant is of that kind which forms a dark 

 velvety mass on the surface of shady troughs supphed with water 

 from cold springs, we have the well-marked band W, and the broad 

 band Y, which is so dark that it almost hides the narrow band X, 

 and thus, as far as that part of the spectrum is concerned, it corre- 

 sponds with the pm'ple Floridea, but difi'ers in the absence of the 

 broad band Z. The presence of the substance which gives the 

 narrow band X is, however, proved by the spectrum of the hght of 

 fluorescence. 



5. The OsciUatoria which grows on damp waUs and ground is 

 perhaps not the same plant as that growing under water, and may 

 belong to the genus Microcoleus of some authors. The spectnun 

 of the pure living plant, separated as described above, shows the 

 band W, and also the narrow band X, without the broad band Y, 

 seen in the case of OsciUatoria grown under water. Much more 

 might be said about the changes that occur at different seasons of 



* See my paper " On the Various Tints of Autumnal Foliage," ' Quart. Joum. 

 of Science ' (New Ser.), i., 1871, pp. 6i-77 ; and that in the ' Quart. Joum. of 

 Micros. Science ' already cited. 



t ' Monthly Micros. Journ.,' iv., 1870, pp. 14-17. 



