364 IOWA ACADEMY OF SCIENCE Vol. XXVI, 1919 



instrument can be inserted into the line of dehiscence and the pollen 

 removed. Such stamens give a more generous supply of pollen than 

 those whose sacs have fully opened. 



A mature or "receptive" stigma has an appearance that is char- 

 acteristic, but not easily described. It becomes somewhat moist 

 looking but the amount of excretion which indicates the receptive 

 stigma is by no means so lavish as in the Lilium species which I 

 have pollinated. However, my experience in dissecting pollen tubes 

 from hand-pollinated Iris stigmas, has convinced me that pollen may 

 germinate when applied to a stigma before it is receptive, although 

 the germination occurs in a shorter time if the stigma is mature 

 when pollinated. I can see no reason why these tubes once started 

 may not effect fertilization. Believing this, I pollinated the stigmas 

 of all the flowers under a given bag while I had it off for the second 

 time, even those I judged to be a little under maturity. I could 

 detect no difference in the subsequent behavior of the individual 

 flowers of the lot. Twenty-four hours after pollination all of the 

 flowers were withered. In withering the blades of the "standards" 

 and the "falls" become soft and limp. Each "fall" in curling, en- 

 folded its stigma, the latter being at that time still turgid and fresh 

 appearing, as can be seen if the withered "fall" is removed. 



Some of the covered flowers were left unpollinated, as checks. 

 A day or two before I left Grinnell for the summer the ovaries of 

 these unpollinated flowers, especially those on pseudocorus, were no 

 larger than when ready for pollination, were slightly yellowed and 

 clearly withering, while those of the hand-pollinated flowers had 

 noticeably grown and appeared vigorous. It looked as though the 

 experiment was prospering, but on my return to Grinnell in Sep- 

 tember I found that the pseudocorus and versicolor had behaved in 

 a markedly different manner. While there were a number of versi- 

 color seed pods with ripe seeds, the promising ovaries of pseudo- 

 corns had nearly all dried and fallen off before maturing and those 

 remaining yielded but one seed that appeared fully developed. 



The cross seems to have succeeded with /. versicolor as the ovule 

 parent but to have failed with /. pseudocorus in that role. It is 

 fruitless to speculate as to the cause or causes of this difference, and 

 the report of the accompanying cytological behavior will have to 

 come at a future date. 



Grinnell College. 



