the Seed in the A Isinoideae. 
27 
In the stages of early development investigation is difficult owing 
to the peculiar orientation of the ovules and the position of the loculi. 
Transverse sections are useless and good longitudinal ones a question 
of luck. For drawings of these stages, therefore, where better preparations 
were available in other species they have been substituted for Stellaria 
media. As the ovules mature, gradual changes take place in the seed coat, 
which result in cuticularization of the cell-walls and infiltration of tannin 
into both the cell-walls and contents of the tegumentary layers. The 
tannin is very resistant to the penetration of paraffin and good microtome 
series are difficult to obtain. For the study of the germination of the seed, 
Cerastium perfoliatum was found to offer a favourable example, as it germi- 
nates easily, and the walls of the seed coat are not so cuticularized and 
contain less tannin than in most other species. 
Three distinct stages seem to mark the comparative development 
of these ovules, viz. :■ — 
1. Pre-fertilization. 
2. Post-fertilization to maturation. 
3. Germination of the seed. 
The descriptive matter has been arranged accordingly. 
In this course of development two long rests occur : — 
(a) in the pre-fertilization stage, immediately after the fusion of the 
two polar nuclei into one definitive nucleus ; 
(b) on the maturation of the seed. 
In explanation of the terms employed, primary megaspore stands 
for the megaspore mother-cell, which develops directly into the embryo- 
sac, since no subsequent tangential divisions of the primary megaspore cell 
were observed. The development of the embryo-sac is thus similar to that 
obtained in many lilies. Primary suspensor refers to the whole of the fila- 
mentous row of cells preceding the actual embryological divisions, which in 
the early stages is usually called the pro-embryo. 
As the inner and outer integuments are each composed of two layers 
of cells, these layers are referred to as layer 1 and 2 of the inner integument 
and layer 1 and 2 of the outer integument respectively, starting from the 
periphery of the ovule. The functions of these two layers, being dissimilar 
in the case of the outer integument and similar in that of the inner, it 
is obviously necessary to differentiate between them. 
The lower portion comprises the base of the nucellus and the chalaza. 
The species investigated were as follows 
A. As far as the definitive nucleus stage. 
1. Alsineae. 
Stellaria Holostea, L., A. media, Cyr., S.graminea, L., A. uliginosa. 
Mum, Cerastium glomeraium, ThuilL, C. quaternellum , Fenzl, 
