187 
The inflorescence is a dichasium. In Zaknum teretifolum it 
is tall and much branched; in 7: xapiforme the stalks are thin and 
wiry; in Z: Greenmanii, the inflorescence scarcely rises above the 
leaves. 
The flowers in Zalnum teretifolium are small (24 in. broad), 
with two sepals or, as some morphologists would have it, two 
bracts and five petals, or a five parted perianth with parts imbri- 
cately arranged. The petals are of a bright rose-purple, ephem- 
eral; stamens 15-20; capsule globular, triquetrous, three-valved, 
many-seeded. The flowers open regularly at a definite time dur- 
ing the flowering period. Darlington, in his Flora Cestrica (3d 
ed, p. 35), says, “ Flowers bright purple, appearing in succession 
opening in sunshine at midday for three or four hours, then 
closing and shriveling.’’ Mr. Meehan observes the same thing 
more accurately. He finds* that its flowers always open regu- 
larly at 1 P. M.; though for one season they closed promptly at 
2, and the next time between 2 and 5 P. M.t In order to finally 
decide the matter as to opening of the flowers in this species, a 
visit was paid by me to a serpentine outcrop near Westtown, 
Chester County, Pa., on June 24, 1896. 
Observations on the spot, the day being warm and bright, 
showed me that the flowers opened between 12:30 and 1 P. M., 
when the flowers were visited by certain hymenopterous insects, 
namely the male of Calliopsis flavipes Smith, and the female of 
Calhopsis andreniformis Smith.t 
The other species of Zal/imum differ from T. teretifolium, as to 
the time of opening of the flowers, so that this peculiarity of the 
plants is specific. E.L. Greene says,§ with reference to 7: humile: 
“ The flowers at 2 o’clock P. M., had not yet opened, hence it is © . : : 
one of those one whose flowers open at evening and closein 
the morning.” Prof. Trelease very kindly had one of his pupils 
make some observations for me on Zalinum patens growing in the - 
Missouri Botanical Garden. In a letter to me, dated Aug. 7, 
1896, he says: “ The flower was fully open at 3:15, and by 4:39 — 
* 1881. Meehan, Bot. Gaz. 6. 280. 
+E. J. Hill, Bot, Gaz, 16: 112. 
tThese insects were determined for me x William ies of the Academy of me 
Natural Sciences, Phila. Re ae 
- § Bot. Gaz. 6: 183. 
