390 Griggs : Characters of the Platanaceae 



In view of these contradictory statements it seemed desirable to 

 undertake a study of the genus for the purpose of ascertaining the 

 facts and of discussing its relationships. When the matter was 

 first taken up in 1905, it was the intention to work out the whole 

 life history of our common sycamore, Platauus occidcntalis L. 

 With this end in view frequent collections were made from October 

 to August and serial sections cut after the usual methods. This 

 intention was frustrated by a severe frost at anthesis, which so in- 

 jured the flowers that only a small portion of them ripened seed. 

 The effects of this injury were entirely internal, however, for the 

 heads all developed alike so that it was not possible to discrimi- 

 nate between the good and the bad until the sections were made 

 — too late to replace the material the same season, and other work 

 has prevented my doing so in succeeding years. The gaps in the 

 life history are so great on this account that it has seemed advis- 

 able to publish only the observations on the morphology of the 

 flower, which perhaps bears more directly on the relationships of 

 the group. 1 here desire to express my thanks to my colleague, 

 Professor John H. Schaffner, for much advice and criticism. 



The head consists of a cluster of flowers so much shortened 

 that the individual pedicels are hard to distinguish. At first 

 sight, even under a microscope, the staminate head in section 

 looks like a single receptacle the whole surface of which is Indis- 

 criminately covered with stamens much after the fashion of a 

 staminate cone of Pinus, a similarity which Is heightened by the 

 resemblance of the stamens of the two, because of the enlarged 

 leaf-like blade of the connective (fig. 2). Closer' scrutiny of a 

 median section (fig. i), however, shows narrow furrows slightly 

 deeper than the general surface of the head, which separate the 

 stamens into groups of one or two (as seen in the section). These 

 furrows are the intervals between the greatly shortened and 

 crowded pedicels which cover the head. This is made more 

 evident by the examination of a tangential section (fig. 4}. Each 

 peduncle, which bears three or four stamens, is surrounded by a 

 circular scale (sc, figs, i, 2, 4), which tapers upward into a fringe 

 of hairs. This is so minute and insignificant that it might easily 

 be overlooked in the abundant hair of the head ; it has no vascular 

 supply and is only two cells in thickness; it develops early and 



