699 
I have obtained no indication which points to this. When I treated 
the crystal platelets got from acetone or alcohol, with dilute sulphuric 
acid for 24 hours at the ordinary temperature I found them un- 
changed and moreover their solubility in various solvents remained 
the same. However this may be, Zorr’s results and mine obtained 
by different methods agree in this that in Haematococcus pluvialis 
more than one carotinoid occurs According to Zorr there are two, 
whilst I have succeeded in erystallising out three in the cells and 
in separating each from the other two. 
Finally I must add a few experimental details. By cultivating 
Haematococcus pluvialis in various solutions, I obtained cultures with 
different aplanospores, both green and red. I cultivated the alga in 
the two following solutions: KNO, 0.01, (NH,), HPO, 0.01, MgCl, 
0.01, Na,SO, (hydrated) 0.01, H,O 100 and NH,NO, 0.02, K,HPO, 
0.02, MgSO, 0.02, H,O 1005. In the former solution most of the 
aplanospores had a green content, in the latter a red one, and this 
was an advantage in the investigation. I used a centrifuge for trans- 
ferring Haematococcus from one solution to another and for washing 
out the material, which sank to the bottom on centrifuging so that 
the solution to be replaced could be poured off. 
It results from this paper and the two previous ones, that my 
conclusions differ completely from those of Tammes and of Konr. 
The assumption, that only one carotinoid occurs in the vegetable 
kingdom, is not based on sufficient evidence. If was the result of 
microscopic and micro-chemical research. Nevertheless I believe that 
such investigation may contribute to our knowledge of carotinoids, 
provided that it be carefully carried out. I have found, for instance, 
that when different carotinoids occur in a plant ov organ, it is in 
many cases at least possible, to distinguish them, that unknown ones 
can be detected (Dendrobium thyrsiflorum) anc that sometimes a 
greater number can be demonstrated than has hitherto been possible 
by other means (Haematococcus pluvialis). The results I have obtained 
are in agreement with the macro-chemical investigation (Urtica dioica). 
When the quantity of material is insufficient for the application of 
other methods, a microscopical and micro-chemical inquiry is still 
practicable and moreover demands comparatively little time. The 
botanist who concerns himself with such work, should however 
consider, that it is impossible to solve by means of a few colour- 
reactions difficult chemical problems, such as, for example, the 
1) H. C. JACOBSEN, |. c. p. 8. 
