228 BIOCHEMICAL SYSTEMATICS 



genera Penicillium and Aspergillus, two and three groups, respec- 

 tively, of quinones are encountered, and within a single group, a num- 

 ber of different quinones occur.) 



The association of anthraquinones with particular families of 

 higher plants is striking. The Rubiaceae, Polygonaceae, and Rhamna- 

 ceae are notable in this respect, with the family Rubiaceae the out- 

 standing example (Hegnauer 1959). Anthraquinones are rare among 

 monocots, having been reported only in the Liliaceae. Schnarf (1944) 

 investigated the presence of aloin in tribes of the Liliaceae. In the 

 tribe Asphodeleae, he found aloin in specialized cells in the genera 

 Asphodelus, Evenurus, Bulbine, Bulbinella, Bulbinopsis, and Alec- 

 torurus. "Aloin cells" are otherwise found only in the tribe Aloineae 

 (except for the presence of chrysophanol in Xanthorrhoea of a third 

 tribe, Lomandreae). Moreover, the above-named genera differed in 

 foliar anatomy and embryology from others of the Asphodeleae but 

 resembled the Aloineae. Thus, according to Hegnauer, the biochemical 

 evidence correlates nicely with embryological and anatomical evidence. 



In a previous study, Munkner (1928) investigated extensively 

 the tribe Aloineae and particularly the genus Aloe. The older tech- 

 nique for the detection of anthraquinones was a color test, the 

 Borntrager test. (A slightly acidified benzene extract is shaken in a 

 test tube with ammonia. A rose red to raspberry color indicates the 

 presence of anthraquinone.) Since it now appears that negative tests 

 with the Borntrager reagent are not always reliable (Hegnauer, 1959), 

 some conclusions based on the presence or absence of anthraquinones 

 by this test might be proven spurious. Of genera related to Aloe, the 

 following results were obtained: 



Gasteria (seven species tested; all positive) 



Lomatophyllum (two species tested; both positive) 



Apicra (four species tested; all negative) 



Kniphofia (ten species tested; all negative) 



Haworthia (seven species tested; two positive and five 



negative) 



One hundred and seventy eight species oi Aloe were examined, 

 and a large majority of the species gave a positive Borntrager re- 

 action. However, there is little indication of a definite pattern of the 

 distribution. For example, although nineteen species of the section 

 Leptoaloe were negative, there were two questionable exceptions 

 {A. kraussii and A. parvula); six of the seven remaining sections had 

 both positive and negative species, as did all but one of the five sub- 

 sections of section Eualoe. 



In the family Polygonaceae, Jaretzky (1926) reported that of 

 the two sub-families, Eriogonoideae and Polygonoideae, only the latter 

 produced anthraquinones. Many species of the genera Ernex, Rumex, 



