JUGLANDACEAE OF THE UNITED STATES. 27 
iiulieato a transition from the Gyninospernis to the An<iio- 
!<})erms, and, by implication, fireut antiiiuity for the groups 
of the hitter in which it occurs. 
In their pollination, the Jniilnndaccat^ ai-c strictly anemo- 
philous.* While the stamin::ic and i>i-tillatc Howers of a 
given tree generally develop Hiiuiltaiu-ou-ly in ///rorm.f 
PringleJ ha^ ch^crvcd a {rwlvnvy to a M'parale <lrx eloj)- 
mcnt of tlie Iwo >oit^ of flou-, r-, and Meehau § >tat(<< that 
in some ca>es a niunhcr of v. arm day. in winter m:IH<-p to 
cause the staminate catkins to de\eU)[> long in a<lvan. c of 
the pistillate tiowers. In Jualans rffjia, Kirchncr :, lia-^ 
noticed that the staminate and pi.tillate tlower^ of a given 
tree develop together, but Meehan !i has observed pro- 
tandry of a month or more on certain walnut trees, after a 
winter with mild days, and De Candolle ** also makes record 
of protandry in this genus. In 1875, Delpino ft called 
attention to the curious circumstance that certain trees of 
the European walnut arc protandrous while others are 
protogynous, a fact commented on by Darwin tt and veri- 
tied for the American J. dnena by p"ringle,§§ in 1879, the 
staminate Howers of one lot of trees blooming simultan- 
eously with the pistillate flowers of others, the other sex 
of both lots also deveIo[)ing synchronously some ten days 
later. Kerner [i H states that the staminate flowers open 
* H. Mueller, Bienen Zeitang, 1882, 23; Engler Prantl, P0an7en- 
familien, iii. (I), 21. 
t De Candolle, Ann. Sc. nat. 4 ser. xviil. 12. On the presumable 
power of sell-fertULzation in the Pecan, -ee Meeiuiu. Eot. Gaz. v. U. 
X Bot. Gazette, iv. 237. 
§ Proc. Phila. Acad. 1885,117. 
isclien Pflanzen, Stuttgart, 1886, 13. 
tt Nuovo Giom. Bot. Ital., vii. 148; Ulteriori Osservazioni, ii. (2), 337. 
%X DifEerent Forms of Flowers, 10. 
§§ Bot. Gazette, iv. 237. 
ill] Verbandl. Zool.-bot. Gesellsch., Wien» 1881, xxsviii. p. 28. 
