POLLEN TUBE AND SPERMATOGENESIS IN IRIS 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 235 
M. Louise SAWYER 
(WITH EIGHTEEN FIGURES) 
This study of spermatogenesis had its origin in an attempt to 
find a satisfactory method of securing prepared as well as living 
material for demonstrating pollen tubes to a class in embryology. 
The fact that it was found possible to dissect out the pollen tubes of 
Iris versicolor, so that tubes of various lengths, developed on the 
stigma and style, became available for study, made it seem advis- 
able to undertake an sph itiat of the pollen tube of this species. 
Tubes were also secured in longitudinal sections of style and stigma, 
and by sowing pollen grains on n culture media. ‘Tubes were grown 
in sugar solutions, the 15-30 per cent proving more satisfactory 
than weaker solutions. A culture medium was made by adding 
30 per cent sugar solution to the sap which oozes from freshly cut 
stalks, and abundantly from the clasping bases of the leaves. The 
superiority of the latter over the pure sugar solution lies i in the fact _ 
that as the tubes grow longer they are less likely, in the cell = oe 
‘sugar solution, to become distorted. Its disadvantage consists in 
the difficulty of freeing the tubes from the gelatinous medium. — : 
Flemming’s stronger solution proved the most satisfactory kill- : 
ing fluid, and iron-hematoxylin has been the favorite stain. 
successful dissection of the tubes is related to the structure of ‘the e : 
Style. That organ arises from the ovary as a single structure, and Lae 
oe at the height of about 1 cm. divides into 3 bra nches. ! 
_ Of a stylar branch (fig. 1) reveal the fact that cach branch is eee an, 
__ ersed by a longitudinal groove. When the flower is re, the 
_— Stylar- rove is vee ee wo | 
