272 BIOCHEMICAL SYSTEMATICS 



methanol test, (2) + for leucanthocyanins, (3) red reaction to 

 "syringin" test, (4) magenta with Ehrhch's reagent, (5) negative for 

 cyanide, (6) negative to "juglone" test, (7) lacking raphides, (8) lack- 

 ing glucitol and sedoheptulose, and (9) oxahs reaction + for cigarette 

 and hot water test. Subsequently, it was stated that, "On the basis of 

 results of these tests, one may propose an Order Hamamelidales, in- 

 cluding the Hamamehdaceae, Platanaceae, Myrothamnaceae, and 

 perhaps the Cunoniaceae." It is not Hkely that proposals for taxo- 

 nomic reahgnment at this level based on such Hmited biochemical 

 data will gather much support for biochemical systematics either 

 from the biochemist or the classical taxonomist. 



Carotenoids: In the preceding chapters certain families of 

 compounds have been selected for special consideration, principally 

 on the basis of their acknowledged or potential contribution to bio- 

 chemical systematics. The decision to devote an entire chapter to a 

 certain class of substances was often wholly arbitrary, though in part 

 supported by the fact that the group of compounds concerned was 

 prominent in the Hterature. The exclusion of some types of compounds 

 was Hkewise arbitrary. The carotenoid pigments were not included in 

 a separate chapter primarily because relatively little attention has 

 been devoted to a study of their systematic distribution. Although 

 certain carotenoids are of very wide distribution, there are neverthe- 

 less many types which are of restricted distribution, hence presumably 

 of systematic value. Since all or almost all plants produce carotenoids, 

 a mere presence or absence notation is meaningless. Yet, there are no 

 simple techniques for the further characterization or separation of 

 mixtures of carotenoids such as exist for flavonoids or even for alkaloids. 

 Goodwin (1955a) noted that the qualitative distribution of caro- 

 tenoids is rather similar among different species of angiosperms. How- 

 ever, xanthophylls are more complex and are of potentially greater 

 systematic value; for example, rhodoxanthin is found in leaves only in 

 gymnosperms. It also occurs rarely in some angiosperm fruits. Goodwin 

 listed twenty-nine anthoxanthin pigments as occurring in higher 

 plants, and undoubtedly a number of others remain to be described. 

 Goodwin (1955b) characterized completely the polyenes of 

 twenty-three species representing eight families and concluded that 

 the distribution of polyenes appeared to be of no obvious taxonomic 

 significance. He stated, "The situation is so complex that many more 

 surveys of the present type will be necessary to reveal possible taxo- 

 nomic correlation." 



Among bacteria and algae, in contrast to higher plants, pig- 

 ments have often been used to support certain phyletic arrangements, 

 and recognition of algal divisions in particular is based upon their 

 chlorophyll, phycobilin, and carotenoid pigment types plus morpho- 



