30 Gibbs . — Notes on the Development and Structure of 
The same author in another paper ( 12 ), 1895, on the c Orientation of 
Embryos in Dicotyledons/ shows that the curvature of the embryo in the 
Curvembryae is due, in the first instance to no mechanical pressure, as 
enclosed for a long period in transitory endosperm, it touches neither peri- 
sperm nor testa. He mentions the small celled suspensor of Spergula 
arvensis , the spiral position of the cotyledons in the mature seed for that 
species and their thick and narrow consistency. 
Holfert ( 20 ), 1890, on the proteid layer (Nahrschicht) in Stellaria 
nemorum , mentions three layers as composing the testa of the seed, viz. 
(1) an epidermis, with wavy cuticle and contracted protoplasm in places ; 
(2) a ‘ Pigmentschicht ’ of tangentially stretched cells with brown contents ; 
and (3) a layer of cells bulging towards the inside, parenchymatous and 
without contents, consequently ‘ Nahrschicht/ as the contents must have 
been absorbed. 
But in Spergula arvensis he gives the sequence of the three layers, 
as (1) epidermis (growing out at intervals into club-shaped hairs), 
(2) ‘ Nahrschicht/ brown and obliterated, and (3) colourless quadrate 
cells (in transverse sections) with pitted walls and brown contents. 
He worked on mature seeds only. 
Balfour ( 27 ), 1901, in his comprehensive address on the Angiosperms, 
throws out some illuminating suggestions as to the function of the integu- 
ments as an integral portion of the sporangium, apart from their ultimate 
purely protective use in the ripe seed. 
He describes the tegumentary system of the ovule as an outgrowth of 
the sporangial primordium of variable origin and development, its primary 
function in Angiosperms is regarded as being that of water jacket and food 
store, developed in response to special demands for water involved in 
the seed habit. 
Finally, Johnson ( 26 ), 1902, in the germination of the seeds of certain 
Piperaceae describes the formation of the endosperm, and calls attention to 
the fact that it is not a storage region, but digests and passes on food 
material to the embryo from the more abundant perisperm or storage 
tissue, and he suggests that this same relation between perisperm and 
endosperm obtains in all seeds with abundant perisperm, such as the Poly- 
gonaceae, Chenopodiaceae, Phytolaccaceae, and Caryophyllaceae. 
Comparative Development of the Nucellus and Embryo-sac, 
as far as Fertilization. 
Stellaria media. 
To study the growth of the nucellus, the very earliest stages in the 
development of the flower must be examined. After the laying down 
