FLORA OF WASHINGTON AND VICINITY. 115 



aud as for below as a poiut opposite Alexauclria, tliougli iu neither of these places 

 did it predoiiiiuate over other forms. 



The fact, however, which most influenced my judgment with regard to its hybridity 

 was the respective dates of flowering of S. nigra and S. cordata. Wlien the latter was 

 fully out in the second week of April, I could see no buds on the former, aud when 

 the anthers of S. nigra were ready to shed their pollen on the first of May, the pods 

 of S. cordata, though empty, were fully developed. The latter bears its flowers 

 before the leaves, the former after, and an interval of three weeks separates the 

 flowering time of the two species. These remarks are not intended as an argument, 

 for it would be arguing without an opponent and against a theory first entertained 

 by myself, but are merely meant to bring out the relations between the forms as niy 

 own observations have revealed them to me. In a highly interesting correspon- 

 dence with Mr. Bebb on this subject, I have expressed my conviction that the fonn 

 has resulted from the normal process of variation from environing influences, and 

 that the co-existence of the variety with the type {S. nigra) is an expression, often 

 observed by me in the case of other plants, of the law which has long been formu- 

 lated by biologists, that variation goes on most rapidly between forms growing in 

 the closest proximity to each other. 



The following is Mr. Bebb's description, which certainly throws all the liglrt 

 upon the subject that is possible in the present state of the investigation: 



" S. NIGRA, Marsh., var. Wardi. Leaves exceedingly variable in outline, the larger 

 lanceolate, roundish at base, obliquely taper-pointed, 4' to 6' or even 7' long by 1' to 

 li' wide, the smaller linear-lanceolate, scarcely |' wide, attenuate-cuspidate, more 

 or less falcate, closely or sometimes slightly and unevenly serrulate, smooth, greeu 

 above, conspicuously glaucous and veined beneath ; petioles short, scarcely exceed- 

 ing the large, reniform, obtuse, persistent stipules; aments terminating lateral 

 branches (the growth of which is continued from the axil of the uppermost leaf), 

 the staminate usually very long, 3'-4', subflexnose, the orange-yellow flowers rather 

 remotely and subverticillately arranged on the slender rachis, scales ovate, obtuse, 

 pale, smooth outside, villous on the inner surface, stamens mostly .% intricately 

 villous at base, mature f rtile ament 3'-4' long by ^' wide, lax, spreading, rachis 

 angular, thinly villous, scales narrower, smoother and caducous; capsules (jnite 

 large, globose-conical, glabrous funder a lens minutely granular); pedicels 4-5. 

 times the length of the nectary; style very short or obsolete; stigmas small, notched. 

 "Staminate aments as in typical «*V/m; lax, fruiting aments i\h hi am;/ gdaloides; 

 leaves varyingin oxit^meijaripaf^sit with nigra but glaucous beneath like amijgdaloides. 

 A peculiar form with leaves proportionately shorter and broader, more remotely 

 serrate and prominently reticulate-veined beneath, might be easily mistaken (in 

 the absence of aments) for an extravagant growth of S. cordata. 



"At first glance our variety Wardi would seem to be a geographical equivalent of 

 the more northern and western S. anu/gdaloides, from which, however, it difiersin 

 the shortly petioled leaves and large persistent stipules— not to mention less tangi- 

 ble characters— and therefore, without venturing to express any ])Ositive opinitm in 

 the absence of reliable data, I am inclined to believe rather that it will be found 

 to connect down the coast with sub. sp. S. longipes of Florida, which in turn passes 

 into the yet more southern ;6f. occidentalis, Bosc. 



"The continued growth of the branchlets bearing the aments, though more or less 

 noticeable in other forms of nigra, is here developed in a renmrk able degree. Thus, 

 before even the staminate aments are fully expanded, not infrequently they are 

 made to appear as if sessile, and opposite a leaf, on the vigorous, growing branches, 

 while a little later in the season the dry persistent rachis of the fruiting ament is 

 found still clinging to the base of branches a foot or more in length.'' 

 Last half of May. 



Salix fragilsxalba, AVimmer. [S. fragiUs, L., var. BmHcUiaiia, Gray^ Manual; S. 

 B It sscUi a )i a, Hmith.'] 



Eastern Branch Marsh, above Benning's Bridge j also, near the Outlet Lock. 



