1888. | BOTANICAL GAZETTE. ISI 
becoming horizontal. The first condition, therefore, which ; 
1s supposed to give rise to zygomorphy is that the flower 
must be large enough to offer some part of it as a landing to 
‘the insect. : 
; to be s 
upper side, and others nototribe with nectaries on the lower 
_ Side? These peculiarities seem to have depended on what 
__, Part of the flower originally offered a landing to the insect. 
_ / Insects seem to prefer the stamens and styles as a lighting 
| ___ Place, and to have used them as such in all cases except those 
__ Imwhich these parts were concealed in a tube. This may be 
9 because these organs were most horizontal, or came in the 
nototribe 
Mate) athe 
Notes on structures adapted to cross-fertilization. 
AUG. F. FOERSTE. 
= (WITH PLATE VIII.) 
_ Silene Pennsylvanica is proterandrous ; the shorter sta- 
first, then the 
, but bees were most frequently observed. 
