HYBRIDIZATION IN IRIS 



M. LOUISE SAWYER. 



In the progress of some cytological studies of pollen tube forma- 

 tion, fertilization and related events/ I became interested in the 

 cytology of hybrids, and determined to make some crosses for the 

 sake of material for a cytological examination of fertilization be- 

 tween parents of different species. Some experience with hand 

 pollination of Iris suggested the choice of that genus for my experi- 

 ment. A survey revealed the fact that of species at my command, 

 there was no pair that have been reported to produce hybrids. Iris 

 pseiidoc'orus and Iris versicolor were available. Their near rela- 

 tionship made it seem likely that crossing might be effected, al- 

 though, so far as I can learn, no hybrids having these parents are 

 known. W. R. Dykes in his magnificent book on "The Genus Iris," 

 which was published in 1912, makes the positive statement that he 

 found no record of that cross having been productive. 



The gross results of an attempt, made in the spring of 1918, to 

 hybridize Iris pseudocorus and Iris versicolor, growing in the botan- 

 ical garden at Grinnell, seem sufficiently interesting to bring to the 

 Academy as a preliminary report. The cytology has not yet been 

 worked out. 



In the experiment, crossing was attempted in both ways : that is, 

 both pseudocorus and versicolor were used as seed parent. There 

 is nothing especially distinctive in the method employed. Inflores- 

 cence stalks were covered with cheese cloth bags before the flowers 

 to be used had opened. The bags were taken off and the stamens 

 removed as soon as the flowers were opened sufficiently to make 

 it possible to reach the stamens with a pair of forceps. This was 

 done early in the morning, say between six and seven o'clock, and 

 the bags were replaced. During the middle of the forenoon pollen 

 was applied to the stigmas. A small scalpel is a satisfactory pol- 

 linating instrument. It is much more satisfactory than a camel's 

 hair brush because more manageable, and less wasteful of pollen. 

 The grains can be scraped from a stamen and applied directly to the 

 stigmatic surface. Even if the pollen sacs are still closed, the stiff 



iPollen Tube and Spermatogenesis in Iris, M. Louise Sawyer, Bot. Gaz. 

 August, 1917. 



