ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 663 



action.* This difference depends, he thinks, specially on the fact 

 that with the previous methods it was necessary to operate on entire 

 plants or leaves. We then have to deal with a greater or less number 

 of superimposed layers of chlorophyll. Those chlorophyll-grains 

 alone which are nearest to the surface receive the light almost un- 

 altered : on those which are deeper down the absorption produced by 

 the first makes its influence felt. But this absorption is chiefly 

 exerted, as is already proved by the microspectral analysis of a single 

 grain of chlorophyll, on the rays between B and C, which, according 

 to Engelmann's experiments, are precisely those which are the most 

 active, as well as the blue at F. On the other hand, the oxygen dis- 

 engaged by the superficial chlorophyll-grains being generally only a 

 small fraction of the total production of oxygen in the plant, it follows 

 that the maximum action of the whole plant can no longer fall between 

 B and C (and at F), but must be displaced in the direction of the green. 

 The justice of this view has also been proved by experiments in 

 which the light, before falling on a cell, has to traverse a thin layer 

 of a solution of chlorophyll. With certain thick cells, very rich in 

 chlorophyll (Cladojihora for instance), the densest accumulation and 

 the most rapid movement of the bacteria may be seen to be above the 

 cell towards the yellow, and below the cell in the red. 



Disengagement of Oxygen by Haematococcus.f — The question 

 whether the red unicellular algae can assimilate without chlorophyll 

 has been lately decided by J. Rostafinski J in the affirmative, for 

 reasons, however, which are not conclusive. T. W. Engelmann has 

 examined this question by the bacteria-method, § and has obtained, 

 even with specimens of a pure red apparently completely destitute of 

 chlorophyll, a very marked reaction on the bacteria. The disengage- 

 ment of oxygen was often tolerably brisk, especially in red light. 

 The comparison of a great number of specimens of different colours 

 showed however that, ceteris paribus, the disengagement of oxygen 

 was so much the more considerable according as there was the more 

 yellow or green observable in the colour of the cells. This gives rise 

 to the presumption, that, even in cells apparently containing only red 

 colouring matter, chlorophyll may still exist. By means of the 

 microspectroscopic eye-piece of Zeiss, it has been found that there 

 is in the spectrum of these cells a dark space corresponding to the 

 chlorophyll-band between B and C. In the cells of the purest red 

 this band was faintly visible only with a particularly favourable 

 illumination ; it became more distinct in proportion to the greener 

 appearance of the cells. 



In view of these facts, it must be admitted that the above-mentioned 

 absorption- band does not belong to the red colouring-matter, but arises 

 from chlorophyll associated with this matter, and it may be considered 

 as very probable that even the entirely red individuals of the genus 

 Hcematococcas only assimilate because they still contain chlorophyll. 



* See amongst others, Pfefi'er, 'Pfknzenphysiologie,'i.(lSSl)p. 211 ctscq., fig, 29. 



t Rev. Internat. Sci. Biol., ix. (1882) pp. 468-9. 



X Bot. Ztg., xxxix. (1SS1) p. 461. This Journal, i. (1S81) p. 930. 



§ See this Journal, i. (1881) p. 962. 



