June 19, 1885.1 



SCIENCE. 



495 



THE GINKGO-TREE. 



An event of considerable interest to botanists 

 has just occurred at Washington in the flower- 

 ing, for the first time, of two of the ginkgo-trees 

 in the U. S. botanic garden. 



In passing the grounds on Saturday evening, 

 Ma}' 6, after the gates were closed, my atten- 

 tion was attracted to a tree standing just inside 

 the enclosure, which, though as yet nearly 

 leafless, was loaded with staminate aments 

 borne in terminal clusters on very short branch- 

 lets all along the branches, even down to the 

 base of the larger ramifications. A glance 

 showed that it was a ginkgo, though I had never 

 seen one in flower before ; and, after examining 

 it sufficiently, I went away, and was obliged to 

 wait until Monday morning before I could 

 notify the superintendent, Mr. W. R. Smith, 

 and institute a search for other trees in the 

 same condition. 



Presuming that, as is usually the case in 

 public gardens and parks, all the trees in the 

 city would also be males, so that no opportu- 

 nity would exist for witnessing the fruiting of 

 this tree, I was most agreeably disappointed 

 when I learned that Mr. A. L. Schott had 

 found another tree in flower in the same en- 

 closure, and that this tree was a female. I 

 thereupon carefully inspected both these trees, 

 and found that anthesis was so nearly synchro- 

 nous in the two sexes that I was able on the 5th 

 to pronounce them ready for fertilization. But 

 as they stand some seventy-five yards apart, 

 with the superintendent's house and other ob- 

 stacles between them, it was evident that this 

 could not take place unaided ; and accordingly, 

 with the hearty co-operation of Mr. Smith, the 

 work of artificial pollinization was undertaken. 

 This has been repeated several times at differ- 

 ent hours of the da}', and so thoroughly per- 

 formed that it is hoped the result will be 

 successful, 1 and that fruit will be borne this 

 season. 



The so-called Japanese ginkgo, 2 or maiden- 

 hair tree (Ginkgo biloba, Linn. ; Salisburia 

 adiantifolia, Smith), is one of the most interest- 

 ing trees that have been introduced into the 

 landscape plantations of Europe and America. 

 Although possessing deciduous foliage and 

 broad green leaves, it nevertheless belongs to 



1 Evidence is abundant (June 15) that artificial pollinization 

 was successful. 



2 The orthography of this word is not settled. Linne 

 (Mantissa plantarura, Holmiae, p. 313) wrote ginkgo, as did 

 also, apparently, Kaempfer before him (Amoenitat. exotic, 

 1712), and as all botanists since have done, and do still ; but near- 

 ly all lexicographers reverse the consonants, and write gingko, 

 usually without explanation. Littre alone, of all I have consulted, 

 gives both spellings. In the supplement to Webster's dictionary 

 the word is said to signify silver-fruit, and it would seem that 

 the etymology ought to determine the orthography. 



the Coniferae, though its affinities with the 

 rest of that family are anomalous, being closest 

 with the yew tribe. An examination of its 

 leaves shows them to be wholly unlike those of 

 any other phenogamous plant. They are del- 

 toid in outline, and the fine nerves that run 

 from the narrow base to the broad apex fork 

 several times in their course, after the manner 

 of ferns. In fact, a ginkgo leaf very closely 

 resembles a much enlarged and thickened pin- 

 nule of the maiden-hair fern (Adiantum) , — a 

 resemblance which not only suggested to Smith 

 the specific name adiantifolia, but has caused 

 the tree to be popularly called in some locali- 

 ties the maiden-hair tree. 



A study of the paleontological history of 

 this remarkable plant reveals the fact that it is 

 an archaic form, and the sole survivor of an 

 otherwise extinct type of vegetation which had 

 numerous representatives in the remote geo- 

 logic past. The Salisburia adiantoides of lin- 

 ger, found in the upper miocene of Senegal, 

 is not essentially different from the living spe- 

 cies ; and Professor Heer detected it again in 

 the miocene strata of Greenland. In 1881 I 

 was so fortunate as to obtain from Laramie 

 strata at Point of Rocks Station, Wyoming 

 Territory, a form which, except for its smaller 

 leaves, appears to be identical with the living 

 one ; and in 1883 I found in Fort Union strata, 

 on the lower Yellowstone, a slightly different 

 form, with larger leaves, showing no lobes, 

 proving that the present living form has come 

 down to us, almost unchanged, from a period 

 as remote at least as the cretaceous age. But 

 other and distinct forms are found in the cre- 

 taceous, and still others, showing greater and 

 greater divergence, as far back as the Jurassic ; 

 those of the oolite bearing clear evidences of 

 having been derived from a series of still older, 

 digitate-leaved forms (Jeanpaulia, Baiera, etc.) 

 whose relationship with the ginkgo was not 

 suspected until these intermediate ones had 

 been brought to light by Heer from the meso- 

 zoic rocks of Spitzbergen and Siberia. In 

 fact, until recently these earlier Jurassic forms, 

 which had been long well known, were from 

 their nervation referred to the family of ferns : 

 as, indeed, a fossil leaf of the ginkgo would 

 probably be now, if the living plant were un- 

 known. 



But even this is not all. By another series 

 of far more ancient forms (Trichopitys, Psyg- 

 mophyllum, Noeggerathia) , this persistent 

 type may be traced still farther back, even 

 across the boundary between mesozoic and 

 paleozoic time, until, in the great carboniferous 

 flora, it has been connected, almost without 



