SEROLOGY AND SYSTEMATICS 



77 



Other data presented by Johnson indicate that inter-specific 

 differences in Magnolia surpass the inter-generic differences in certain 

 cases. For example, the heterologous reaction between Magnolia 

 tripetala and M. portoricensis is 53.6 while the heterologous reaction 

 between Magnolia virginiana and Michelia champaca is 83.0. In fact, 

 the latter heterologous reaction is greater than many heterologous re- 

 action among species of Magnolia tested against M. tripetala antisera. 

 Since, apparently, similar procedure was used in all cases, it is difficult 

 to account for this apparent paradox, even when it is recognized that 

 different host animals were used which may differ in their antibody 

 responsiveness. The same type of situation is noted in Baum's work. 

 Unfortunately no explanation of this is presented in the original pub- 

 lications. In this connection an interesting statement in a discussion 

 of serological work on songbirds seems pertinent: 



An additional point to consider in the interpretation of these [serolog- 

 ical] tests is that the techniques used tend to separate more sharply 

 species that are closely related, while species distantly related are not 

 so easily separated. In other words, comparative serological studies 

 with the photronreflectometer tend to minimize the differences be- 

 tween distant relatives and to exaggerate the differences between close 

 relatives. (Stallcup, 1961.) 



This remarkable statement provides for a somewhat confus- 

 ing situation wherein, in the interpretation of data, one doesn't know 

 whether to consider two species farther apart or closer together than 

 the data indicate. If Stallcup's generalization is supportable, then cer- 

 tain taxa, of problematical familial alliance, such as Hydrastis (to be 

 discussed below), would be almost incapable of placement by ser- 

 ological results. 



Hammond (1955b) compared a number of genera in the 

 Ranunculaceae on the basis of their serological interactions, and this 

 criterion, together with cytological and morphological data, was used 

 to produce a new systematic treatment of the genera. According to 

 Hammond the family is "serologically close-knit," and he considers 

 this observation to be in contradistinction to the generally held view- 

 point that certain genera of the family are relicts of ancient evolu- 

 tionary lines and thus genetically quite distinctive. The basis of Ham- 

 mond's statement is, however, not clear, since only a few families of 

 flowering plants had been studied at that time, and furthermore a 

 number of genera which he tested gave no reaction to the antiserum. 

 Hammond produced a three-dimensional model to depict the serological 

 relationships within the Ranunculaceae. Notable among his conclu- 

 sions is the placement of Hydrastis into the Ranunculaceae on the 

 basis of a positive reaction with Aquilegia antiserum. Hydrastis has 



