SEROLOGY AND SYSTEMATICS J] 



protein extract from one plant is twice as concentrated as that of 

 another, should they be adjusted to a standard concentration for 

 vahd comparison? Dissenters would note that it has not been estab- 

 lished that there is a necessary correlation between total protein and 

 antigenic activity. It has been suggested that a constant ratio of 

 tissue to solvent is preferable. 



Injection of the extract into the host is intraperitoneally, 

 intracutaneously, or intravenously. A typical inoculation schedule 

 might be 5 cc doses administered at three to four day intervals with a 

 total of five to eight injections followed by a nine to ten day rest 

 before bleeding (Chester, 1937). It may be noted that individual 

 differences in the reactivity of different host animals, while reduced 

 by careful breeding, can never be entirely ehminated. Consequently, 

 some of the differences in serological reactions must represent 

 variations in host reactivity. This factor is undoubtedly taken into 

 account by workers in serology but is not often expressed. The com- 

 plications stemming from the requirement of a supply of host animals 

 have probably deterred many botanists otherwise receptive to 

 serological investigations. If the "Kunstsera" (artificial serum from 

 beef) reported by Mez had proven as reliable in the hands of other 

 investigators as claimed by its developer, we might have witnessed a 

 dramatic adoption of the serological approach. 



In the earlier serological investigations, there were two differ- 

 ent methods of reading the precipitin reactions. As usual, one was 

 favored in Berlin and one in Konigsberg. The first of these, the 

 "flocculation test" was utilized by the Mez group in Konigsberg. In this 

 technique a carefully diluted antigen solution was mixed in a standard 

 sized test tube with an aliquot of undiluted antiserum. The mixture 

 was shaken, incubated for a standard time, and the height of the 

 precipitate which had, in the interim, flocculated, was read. The 

 observer, by design, did not know the identity of the serum being 

 tested. The second method was called the "ring test." In this test the 

 denser liquid was added to a test tube and the less dense liquid 

 pipetted carefully onto its surface. Without disturbing the layers, the 

 tube was incubated under standard conditions and the width of the 

 ring of precipitate measured. The ring test is not used frequently 

 at present, but Lewis (1952) has used this test in studies of the sero- 

 logical manifestations of pollen incompatibility factors. 



A final commentary on the rather unfortunate controversy 

 between the Konigsberg and Berlin groups may be appropriate at this 

 point before passing to the post-Chester period in plant serology. 

 Chester felt that the controversy was to a considerable degree respon- 

 sible for the failure of systematists to become receptive to the 



