450 
Sargant . — The Formation of the 
TABLE I. 
III. 
IV. 
V. 
Buds. 
I. Buds sessile. 
/ Pedicels begin to 
grow. 
jj J Buds io-ii mm. 
* 1 long. 
I Anthers green and 
l sessile. 
/Filaments begin to 
) grow. 
j Anthers yellow to 
l orange. 
S Buds about 20 mm. 
long. 
Anthers deep orange. 
Buds 20-30 mm. 
long. 
VI. 
Flower opens. 
Anthers dehisce. 
Spermatogenesis . 
Archesporial divisions. 
Pollen mother-cells dif- 
ferentiated, resting nu- 
cleus. 
Formation of spirem thread 
in pollen mother-cells. 
First and second nuclear 
divisions in pollen 
mother-cell (1, 2). 
Vegetative division in pol- 
len grain (3). 
Division of generative nu- 
cleus in pollen-tube (4). 
Oogenesis. 
Nucellar divisions. 
Embryo sac differentiated, 
resting nucleus. 
F ormation of spirem thread 
begins. 
Spirem formed. 
First and second nuclear 
divisions in embryo sac 
(1,2). 
Four equal nuclei in em- 
bryo-sac. 
Nuclei differentiated in 
pairs. 
Third nuclear division in 
embryo-sac (3). 
Methods. 
The methods of the histologist are necessarily indirect. 
He is seldom able to observe the structures he describes 
while they are alive. His only resource is to arrest their 
movement by killing them as instantaneously as possible, and 
from a series of the figures thus obtained to attempt a recon- 
struction of the process of growth. It is therefore essential 
to bear in mind the possibility of errors arising (1) from 
deformation produced by the processes of preparation, and 
(2) from faulty sedation. 
Owing to the mass of material dealt with, I have found it 
impracticable to use consistently more than two fixing 
methods. My preparations however are in two parallel series 
