H. MARSHALL WARD. 
]4 
lirely different shoots, or even on other plants than those which 
bear the female sexual organs. Each pollen grain on ger- 
mination (a process which by special appliances is brought 
about in close proximity to the female apparatus) emits a 
tubular body, in which indications of division occur, while a 
very few divisions are also established in the interior of the 
pollen grain itself. It is now generally accepted that the 
internal divisions represent a prothallium even more reduced 
than that of Selaginella, while the pollen-tube contents must 
be regarded as the representative of what becomes anthero- 
zoids in vascular Cryptogams — structures which are here 
rendered unnecessary as such, by arrangements already 
referred to. Instead of shedding motile antherozoids, there- 
fore, the pollen grain carries its sexual products right into 
the region of the oosphere by means of the pollen-tube. 
In the female apparatus we find the same principles of - 
suppression carried still further ; the macrospore^ or '^primary 
embryo-sac '' is never shed at all, but germinates, so to 
speak, inside its sporangium — the so-called nucleus of the 
ovule. 
During the gradual discovery of the phenomena which we 
are discussing, a number of synonyms have been introduced 
into the nomenclature, and some confusion is apt to arise in 
comparing these processes with what occur in Cryptogams ; 
hence no apology is offered for the following summary : 
The archegonia (the oosphere'S of which are the corpus- 
cula of R. Brown, the secondary embryo-sacs^’ of Hen- 
frey) are formed by division of peripheral cells of a delicate 
prothallium formed of large, thin-walled, polygonal cells, 
and termed endosperm this prothallus arises in the 
protoplasm of a cavity which appears like an enlarged 
cell ^ of the nucleus of the ovule, and is the primary 
emhryo-sac.” From its bearing archegonia and other rela- 
tions, we must regard this endosperm ’’ as an internal 
prothallium similar to that which arises in Selaginella before 
the endosperm ” of that plant is formed ; the term endo- 
sperm” has been applied, therefore, to two structures which, 
whatever relations they may have morphologically, are dif- 
ferently distributed in time. The endosperm ” of Selaginella 
arises after the prothallus of that plant is formed, and coexists 
with it at the period of fertilisation ; the endosperm ” of 
Conifers is the prothallus, and bears the archegonia. 
The archegonium of Conifers consists of an oosphere, with 
^ Or possibly several. 
- And was so described by llofmeister. But cf. Strasburger, ‘Die 
Angiosp. u. Gjfinuosp.’ 
