440 ^ CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



Liliaceae and Iridaceae. The chlorination of lignin (Maiile reaction) has been 

 used as a specific test for angiospermons wood. It is of interest that all three 

 genera of Gnetales give a similar reaction (McLean and Evans, 1934; Gertz, 

 1943), but the phj^logenetic implications of this striking fact are weakened by 

 the discovery that one out of seventeen species of Podocarpus treated gave a 

 weak but positive reaction, also (Crocker, 1933). 



McNair, in a series of papers (1934, 1935a, 1935b, 1942, 1945a, 1945b), has 

 attempted to establish correlations of chemical changes with the degree of evolu- 

 tionary advancement of the plants in which the chemical substances occur. Thus 

 he states that with phylogenetic specialization : ( 1 ) unsaturated oils tend to in- 

 crease at the expense of saturated ones; (2) the size of molecules tends to in- 

 crease, the molecular weight of alkaloids increases, and the specific gravity of 

 volatile oils mounts while their index of refraction declines; (3) the number 

 of fatty acids in fruit and seed fats tends to increase; (4) the heat of combus- 

 tion of fatty acids and alcohols increases; (5) the iodine values of giycerides 

 increases; and (6) the orientation of hydrocarbons tends to shift from dextro- 

 to laevulo-rotary. On the basis of these postulates, he concludes that apocarpy, 

 choripetaly, and woody habit are more primitive than syncarpy, sympetaly, and 

 herbaceous habit, that Magnoliaceae are more primitive than Ranuneulaceae or 

 Berberidaceae, that oligocarpy is at least as archaic as polycarpy, and that mono- 

 cotyledons are older than dicotyledons. 



The most spectacular results and the hottest controversy have come from 

 the serological testing of protein specificity as providing clues to affinity, and 

 culminating in the famous "Konigsberger Stammbaum" (Mez and Ziegenspeck, 

 1926). The literature, especially German, of the 1920's and 1930's is replete 

 with criticism, counter-criticism, and polemic between adherents of the various 

 "schools" of serology (Worseck, 1922; Mez and Ziegenspeck; Gilg and Schiirhoff, 

 1926; AVermund, 1928; Moritz, 1929, 1934; Roederer, 1930; Ruff, 1931; Krohn, 

 1935; Mez, 1936). The degree of positiveness on both sides is striking and ap- 

 pears to conform very poorly with scientific objectivity. The following quota- 

 tion may be regarded as not wholly atypical (Krohn, 1935, pp. 370-371). 



Accordingly all conclusions derived from serological species-reactions must be taken 

 as conclusive for the relationship of the whole families. . . . Morphology and serology are 

 never in contradiction, in the contrary they are furnishing reciprocal corroborative 

 results. ... My control-tests are supporting the present classification of the Konigsberg- 

 Genealogical tree, in opposition to the publications of the Berlin School. 



Chester (1937) has reviewed the subject of the serological approach to plant 

 relationship with sympathy, indicated his faith in its theoretical soundness, and 

 suggested that differences in method might account for the conflicting results 

 obtained by different workers. He also stressed the fact that plant antigens are 

 the consequence of a whole mosaic of individual reactions and should, there- 

 fore, afford a superior measurement of relationship. By the comparison of iso- 

 electric points of latex proteins, Moyer (1934a, 1934b, 1936) has attempted to 

 determine species affinities and to correlate the position of isoelectric points with 

 chromosome number in Euphorhia and Asclepias. 



Redfield supplied a needed caution against the too exuberant application 

 of chemical characteristics to phylogeny, in the following words (1936, p. 122) : 



Much of physiology is by nature analogous — being the fortuitous combination of 



