Io BOTANICAL GAZETTE [JULY 
though usually, so far as accounts go, the final separation for the 
reduction does not occur until the second division. In Arisaema 
the mode of tetrad formation by longitudinal and transverse 
division is such as to effect reduction in the prophase of the first 
division, while during metaphase and anaphase the reduction is 
completed by the separation of the tetrad of the transversely 
divided diad. 
II. REDUCING DIVISION OF THE CHROMOSOMES IN 7R/LLIUM 
GRANDIFLORUM DURING SPOROGENESIS. _ 
In studying the development of the pollen of 7yil/ium grandi- 
florum, the chromosomes were found to be of such large size as 
to offer, possibly, a good opportunity for an investigation which 
might throw some light on certain of the problems of mitosis 
during sporogenesis. The preliminary studies were made upon 
material collected during the autumn and winter of 1896-7. 
With the experience of one season’s work it was possible to plan 
for the collection of a quantity of material in different stages of 
development. The young flowers of Trillium begin their develop- 
ment in Juneand July ofthe previous year, and by autumn they are 
well formed, though they remain protected in the sheathing bud 
scales during the winter. So far as I have found, the arche- 
sporium is completed and the period of growth of the pollen 
mother cells is closed with the oncoming of winter, if not before. 
The period during which the division of the pollen mother cells 
takes place extends over seven or eight months. This is due 
not only to some variation in the time of maturing of different 
plants in different localities, but also to temperature. In the open 
woods, on rather high ground, where the plants are protected 
from cold north and west winds and are exposed to the warmth 
of the sun, the pollen is often mature in the latter part of 
September. In the cool ravines and open places exposed to 
north winds, the pollen is formed in warm days during February, 
March, or April, according to the season, and to some extent 
also according to the state of maturation in different individuals. 
Very cold weather checks the progress of mitosis, but when 
