CONIFERS. 
to a section of a young sporangium of Lycopodium : the archesporium consists 
in both cases of a group of cells bounded by a tapetal layer. There is reason, 
inasmuch as their mode of development is the same, to regard these cells in the 
Cupressineae as being, like the archesporial cells of Lycopodium, spore-mother-cells ; 
but whereas in Lycopodium each of these mother-cells produces four spores, in 
the Cupressineae only one of them persists and it produces only one spore, the 
embryo-sac. The embryo-sac is then the equivalent of the macrospore of the 
heterosporous Vascular Cryptogams. 
In the Abietinese, the archesporium has become much reduced as compared 
with that of the Cupressineae. The Cupressineae resemble the higher Vascular 
Cryptogams in the mode of development of the ovule and embryo-sac, whereas the 
Abietineae approach the Angiosperms.] 
Develop?nent of ihe Endosperm (Prothallium). The first stage in the development 
of the endosperm is the division of the nucleus of the embryo-sac ; each of the two 
nuclei divides again, and this process is repeated until a number of nuclei have been 
formed which lie in the peripheral protoplasm. Around each nucleus the protoplasm 
becomes marked off by an ectoplasmic layer, cell-walls are formed, and thus one 
or two layers of endosperm-cells are formed in the embryo-sac in contact with its 
wall. These cells grow in the radial direction, and divide in such a manner that 
the embryo-sac is filled with parenchymatous tissue. In those Coniferae in which 
the seeds take two years to ripen, as Pinus sylvestris and Juniperus communis, 
the endosperm formed in the first summer is again absorbed in the spring, the 
protoplasm of the primary endosperm-cells is set free by the deliquescence of their 
cell-walls, and forms by division a number of new cells which, in May of the second 
year, again fill with parenchymatous tissue the embryo-sac now considerably in- 
creased in size. 
The archegonia (corpuscula) are developed, according to Strasburger's obser- 
vations, from superficial cells of the prothallium (endosperm) in the same manner 
as the archegonia of the highest Cryptogams. The mother-cell increases in size 
and is divided by a septum parallel to the surface of the investing embryo-sac ; 
a large inner (lower) cell is thus formed, the central cell of the archegonium, and 
an upper small one, lying next the embryo-sac from which the neck of the 
archegonium is formed^. In Abies canadensis this neck remains simple and uni- 
cellular, and elongates considerably with the increase in size of the surrounding 
endosperm ; but usually the original cell which constitutes the neck divides into 
several cells which either lie only in one plane (Figs. 354 A, d, 355 /, d), the 
' stigmatic cells,' or form several layers lying one over another (as in Abies excelsa 
and Pinus Pinaster^, Seen fipm above the neck appears to form a four-celled, 
or, in Abies excelsa, even an eight-celled rosette. The homology of the ' corpus- 
culum ' with the archegonium of Vascular Cryptogams, already established by the 
earlier investigations of Hofmeister, is carried a step further by Strasburger, who 
discovered the formation also of a canal-cell. He considers that the part of the 
protoplasmic contents of the large central cell which Hes immediately beneath the 
^ Hofmeister (Vergleichende Untersuchungen, p. 129) gives a somewhat different account of the 
origin of the archegonium [Germination, &c., p. 410]. 
