80 . BIOCHEMICAL SYSTEMATICS 



With an antiserum prepared from S. tuberosum the Mexican 

 species could be divided into three groups: one gave four precipitin 

 lines, another two lines, and the third one line. (All South American 

 species give reactions similar to S. tuberosum.) One aberrant epiphy- 

 tic species, S. morelliforme, yielded only one line, but in addition this 

 line could not be further resolved into two lines as was the case with 

 a precipitin line in a similar position in the other fourteen species. 

 Therefore, serologically, S. morelliforme appeared farthest removed 

 from S. tuberosum. In some comparisons, notably in strains of S. 

 polytrichon, differences within a species proved greater than those be- 

 tween species. 



Species of Series V and VI without exception yielded two lines 

 with S. tuberosum, antiserum and further showed a similar pattern 

 against antiserum of one of the Series V species (namely S. ehren- 

 bergii) and even a moderately close relationship to species of Series 

 IV and XIII. Thus the authors consider Series V and VI to be a link- 

 ing group between the two pairs of series mentioned. 



All other species were grouped together when tested against 

 S. tuberosum, but against S. ehrenbergii (preadsorbed with S. tubero- 

 sum) only S. tuberosum, S. verrucosum and S. semidemissum were 

 placed together (showing no precipitin lines). 



Series XII, XIII, and XIV, which gave four-Hne patterns 

 against S. tuberosum, have in common an important morphological 

 feature, the rotate or wheel-shaped corolla, while the other series 

 have a stellate corolla type. (South American species have, also, the 

 rotate corolla.) Furthermore, crosses within Series XII, XIII, and 

 Series Tuberosa can be made as well as between Tuberosa and various 

 South American species. Series Bulbocastana, which also gave a four- 

 line pattern with Tuberosa, is exceptional in that it does not hybridize 

 with species of the other Series readily. Finally, Series V and VI, 

 giving the two-line spectrum, are fairly interfertile. Although the 

 results should prove to be interesting, reaction patterns to specific 

 antisera of all species concerned were not reported. 



In general, the serological data from Solarium follow rather 

 closely the patterns of morphology and hybridization. The fact that 

 the type of serological methods used by these authors provides a 

 pattern in accord with other lines of evidence lends validity to the use 

 of the method in systematic studies. It is interesting that immuno- 

 electrophoretic studies generally yield only a relatively few arcs of 

 interaction, even though no preadsorption is carried out. From pre- 

 cipitin reactions one gains the impression that a large number of 

 antigen-antibody interactions are involved in a single precipitin reac- 

 tion. It is probably that in Immunoelectrophoresis, when crude extracts 



