June, 1937 



EVOLUTION 



Page Eleven 



species. When, in addition, consideration is given to the 

 extreme modifications developed through secondary and 

 further variation in this same group of ferns, resulting -n 

 scores and scores of well distinguished varieties, a new 

 understanding should attach to the meaning of \ariation 

 as a process and its underlxing significance in evolution. 





FIGURE 3. Piniiae of Boston Fern and seven primary 

 mutations, arranged as in Figure 2. 



Dozens of new forms ha\e appeared in the Brooklyn 

 Botanic Garden during the years of experimental culture. 

 Four kinds of variation are represented among these prim- 

 ary sports of the Boston fern ( I ) increase in division, from 

 once to twice pinnate; (2) dwarfing: (^) increase in ruf- 

 llmg; and (4) cresting. 



The second and third leaves represent increased leaf 

 division. The third leaf is from the ".\nna Foster" variety, 

 the earliest of all the Boston fern sports. The "Pierson" 

 fern is shown in the second leaf and pinnae. From this 

 form alone, scores of secondary, tertiar\' and higher degree 

 sports have developed, resulting in various degrees of leaf 

 division — up to five pinnate, — and other modifications. 



The fourth and fifth leaves and pinnae represent 

 dwarf types, "Scott's" fern (of Brooklyn origin) and the 

 Giatras fern. In addition to their smaller size, each 

 offers other differences in outline, marginal characters, and 

 configuration of the pinnae, and in the habit of growth. 



The sixth and seventh leaves and pinnae present in- 

 tensification of the ruffling or waving of the pinnae, horti- 

 culturally known as crisping. The larger leaf (6) is called 

 the 'Harris" fern; the other the "Roosevelt". Lastly, there 

 is a crested or "fishtail" type of variation, which occurs 

 not infrequentl\ in wild native species. In the Boston fern 

 series this variety first appeared in Louisiana, and takes 

 its name from the town of its origin, "Gretna ". 



That evolution must have occurred by means of in- 

 herited \ariations will he accepted as axiomatic. The 

 student who has examined material of the kinds present- 

 ed here will form a clearer conception of what is meant 

 by variation, and a better understanding of the relation 

 of this process to evolution. 



From Torreya 30 : 145-152. Brooklyn Botanic Garden 



Evoluiion Remains Darwinian 



Rv HENSHAW WARD 



A recent editorial in the New Vork 

 Times entitled Darwin Fifty 

 "> ears After," contained these two sen- 

 tences; "Research conducted within the 

 last decade has shown that almost im- 

 perceptible mutations are the ones that 

 count in evolution, and that by selection 

 their direction and preservation are de- 

 termined. So we come back to Darwin's 

 own Darwinism." The Times is not an 

 authority on biology, but it indicates the 

 Trend of recent conservative thought, lis 

 editorial is proof that the greatest hind- 

 rance to popular acceptance of Darwinism is disappearing. 



That hindrance was the doubt which some biologists 

 felt about Natural Selection. The doubters (mostly stu- 

 dents of genetics) were wont to express themselves thus; 

 "Though we have no doubt of evolution, we suspect that 

 Darwin's theory ma)' not be the right explanation." The 

 suspicion was interpreted b\' many literary and philos- 

 ophical minds to mean; 'Darwinism is in a bad way." 



Even if Darwinism had died, the evolution theory 

 would not have been disturbed. But the theory can be 

 much rhore readily accepted by the general public, and 

 can do its work in education more smoothly, if it does not 

 have to encounter the perpetual query, "But isn't Darwin- 

 ism disputed?" During the last few years so many author- 

 ities have spoken so strongly in support of Darwinism that 

 even the Times is persuaded. 



The most important element of Darwinism is Natural 

 Selection — the theory that in the hard struggle for existence 



Has the Darwinian Theory 

 of Natural Selection been 

 discarded by scientific men 

 as fundamentalists so often 

 profess to believe? Do the 

 latest facts disprove the evo- 

 lutionary theory? Dr. Ward 

 answers by quoting the opin- 

 ions of modern scientific 

 authorities. 



the fa\orable variations are preserved in 

 heredit)-, and that there is thus a gradual 

 alteration in a species which adapts it 

 better for successful living. A less im- 

 portant element of Darwinism, but one 

 that has loomed large and has seemed 

 vital to many reasoners, is the theory 

 that the principal material of evolution 

 has been the small variations. Critics 

 of Darwin have been dubious about the 

 power of Natural Selection, and they 

 have assumed that Darwin's small vari- 

 ations have been supplanted bv the large 

 sporting mutations such as de "Vries described. 



The following quotations indicate how general and 

 thoroughgoing is the sweep of recent biological thought 

 toward Natural Selection and toward the conviction that 

 no modern investigation of "mutations" has furnished 

 anv substitute for Darwin's conception of inheritable vari- 

 ations, whether small or large. 



I. Prof. H. J. Muller is the most natural man to quote 

 first; — "Data on the actual occurrence of mutations support 

 Darwin." He knows. His investigations of mutations 

 by .\-rays are so highy respected that he was chosen by 

 the Britannica to write the article "Variation". In that 

 article he declares: "Geneticists are returning to a view 

 essentially similar to Charles Darwin's — namely, that the 

 origin of one species from another involves the accumula- 

 tion of numerous selected small steps of heritable varia- 

 tion." Since it was the geneticists who used to raise most 

 doubt about Darwin's conception oY variation, there is 



