522 
yellow ones appeared. In one of the yellow variegated leaves, namely, 
of Graptophyllum pictum I obtained the separation of small orange- 
yellow erystals in the yellow portion of the leaf. The erystals which 
had separated behaved towards reagents and solvents exactly as 
did the corresponding erystals obtained by the potash method. 
With regard to the investigation of flowers with dilute acids, 
Tammes’ *) results and mine differ. Whilst she obtained well formed 
crystals in all cases, I obtained them only exceptionally. Our in- 
vestigations were however mostly concerned with different flowers. 
I propose if possible to examine with acids those flowers which 
have been studied by Tames, but not yet by myself, in order to 
reach greater certainty on this point of difference. Whatever the 
ultimate results, I nevertheless already venture to state, that the 
method of inducing crystallisation of the carotinoids in plants by 
means of acids cannot in general be recommended. Often the yellow 
carotinoids in particular do not crystallize. Red crystals very often 
form in the tissue but not in all cases in which they can be obtained 
by the use of the potash method. This is the case, for example, in 
the flowers of Nuphar luteum, Isatis tinctoria, Cytisus Laburnum and 
Thermopsis lanceolata as also in the peduncles of Trollius caucasicus. 
In these many oranje-yellow and a few red crystals were obtained 
by Moriscu’s reagent, whilst in the flower of Asclepias curassavica, 
in which, as stated above, red crystals had been separated out by 
means of acids, Mortsca’s reagent produced many red as well as a 
few orange-yellow crystals. When the carotinoids which yield red 
crystals are present in great quantity, they can therefore be demon- 
strated by acids, but when they are present in small quantity, they 
escape observation. 
Another drawback to the acid method is that the carotinoids 
which yield orange-yellow crystals are very liable to decompose. 
Continuous treatment with acids as is necessary with the acid 
method, often is very harmful and may lead to complete decom- 
position of the carotinoids. They are much more liable to decompo- 
sition by acids, while they are still in solution in the fatty substance 
of the plastids, than when they have been separated as crystals 
by some other method. According to HUsrMANN ®) WACKENRODER 
pointed out this decomposition so far back as 1832. In the treatment 
with acids I have sometimes found decomposition to occur even in 
the first few days. The colour of the flowers becomes paler and the 
i) ie: p. 243. 
2) A. Husemanny, Über Carotin und Hydrocarotin, Ann. der Chem. u. Pharm. 
Bd. CXVII, 1861, p. 200. 
