JUGLANDACEAE OF THE UNITED STATES. ai 
indicate a transition from the Gymnosperms to the Angio- 
sperms, and, by implication, great antiquity for the groups 
of the latter in which it occurs. 
In their pollination, the Juglandaceae are strictly anemo- 
philous.* While the staminate and pistillate flowers of a 
given tree generally develop simultaneously in Hicoria,t 
Pringle { has observed a tendency to a separate develop- 
ment of the two sorts of flowers, and Meehan § states that 
in some cases a number of warm days in winter suffice to 
cause the staminate catkins to develop long in advance of 
the pistillate flowers. In Juglans regia, Kirchner || has 
noticed that the staminate and pistillate flowers of a given 
tree develop together, but Meehan J 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 ff called 
attention to the curious circumstance that certain trees of 
the European walnut are protandrous while others are 
protogynous, a fact commented on by Darwin ff and veri- 
fied for the American J. cinerea by Pringle,§§ in 1879, the 
staminate flowers of one lot of trees blooming simultan- 
eously with the pistillate flowers of others, the other sex 
of both lots also developing synchronously some ten days 
later. Kerner |||| states that the staminate flowers open 
explosively. 
* H. Mueller, Bienen Zeitung, 1882, 23; Engler & Prantl, Pflanzen- 
familien, iii. (1), 21. 
+ De Candolle, Ann. Sc. nat. 4 ser. xviii. 12. On the presumable 
power of self-fertilization in the Pecan, see Meehan, Bot. Gaz. v. 11. 
t Bot. Gazette, iv. 237. 
§ Proc. Phila. Acad. 1885, 117. 
|| Neue Beobachtungen uber die Bestiubungseinrichtungen einheim- 
ischen Pflanzen, Stuttgart, 1886, 13. 
q v.c.117. 
mt. Ce Ds 12. 
tt Nuovo Giorn. Bot. Ital., vii. 148; Ulteriori Osservazioni, ii. (2), 337. 
tt Different Forms of Flowers, 10. 
§§ Bot. Gazette, iv. 237. 
||| Verhandl. Zool.-bot. Gesellsch., Wien, 1887, xxxviii. p. 28. 
