156 Bliss— A Contribution to the Life- history of Viola. 
open. From this point, flowers from one to five days open and withered 
flowers were collected. The buds collected in Philadelphia were measured 
for greater accuracy. 
In order to determine the exact age of a flower at a certain stage of 
structural development, the buds were tagged in the open field with a tiny 
square of white paper tied to the stem by a thread. For instance, fifty 
buds which were to open the next day were tagged with the number 1, 
and this number with date of tagging was recorded in a notebook. The 
next day some of the flowers were collected and fixed ; others from the same 
group were collected on the second and third days and so on. In this way 
about a thousand violets were tagged and collected. The following table 
shows stages of structural development and relative size of bud or age of 
open flower. 
Table showing Relative Size of Bud and Stage 
of Development. 
Buds . 
Buds smallest, colourless. V. cucullata. 
Buds medium, green. V . pedata. 
Buds small, green. V. odorata. 
Buds large, corolla not visible. V. cucullata. 
Buds large, corolla visible. V. cucullata. 
Buds large, corolla not visible. V. pedata. 
Buds just opening. V. cucullata. 
Buds just opening. V. Jimbriatula. 
Buds just opening. V. pubescens. 
Flowers first day open. V. cucullata. 
Oogenesis. 
Placenta differentiated. Ovular papillae 
not yet visible. 
Ovular papillae developed. 
Ovule nearly anatropous ; integuments 
visible, archesporial cell differentiated, 
tapetal cell cut off. 
Second division of tapetal cell. Mega- 
spore - mother - cell in prophase of 
division. 
Growth of functional megaspore. 
Two=£elled embryo-sac. 
Four-celled embryo-sac. 
Eight-celled embryo-sac. 
Fusion of polar nuclei. 
Presence of pollen-tubes. Stages in 
fertilization. Division of endosperm. 
Two fixing fluids were used, Flemming’s chrom-osmo-acetic acid and 
chrom-acetic-acid solutions. Both gave good results. The pistils were 
removed from the bud and the ovaries only fixed. The wall of the larger 
ovaries was cut away so that the fixing fluid might penetrate more quickly 
to the ovules. In some cases, the style was left in position in order that 
the path of the pollen-tube might be traced. Some of the buds collected 
were so small that it was impossible to dissect out the ovaries. These buds 
were fixed whole, and in section offer an interesting comparison of relative 
microsporangial and macrosporangial development. Two stains, Flemming’s 
triple stain and Heidenhain’s iron-alum haematoxylin, were used. Both 
gave good results. 
