192 SECTIONAL ADDRESSES. 
usual manner, the antheridia, instead of producing single antherozoids, 
contain a large number of very small, motile sperms. The oogonium is an 
outgrowth of an intercalary cell, which becomes separated by a wall and 
is finally detached. Ikari,’ in his account of Laminaria religiosa, describes 
the antheridia as forming a continuous row, with a common opening in 
the terminal part of the row. This may, perhaps, help to explain the case 
of Phyllitis. : 
Two characteristics of the spore germination in all the Laminarias 
_ investigated are :— 
1. The formation of a tube through which the cgntents of the spore 
migrate into the new bulbous enlargement. 
2. The division of the spore nucleus, and (except in rare cases) the 
degeneration of one of the daughter nuclei. 
One wonders whether these constantly recurring features have any 
significance in the life-history. One writer suggests that the nuclear 
division establishes sexuality. But what exactly does that mean ? 
There is no time to enumerate the additional genera whose gameto- 
phytes have been identified by different observers, but in all cases the 
difference in size between the two generations is startling. To see 
fertilisation actually taking place is more a matter of chance than any- 
thing else ; and, so far as is known, the writer is the only one who has been 
lucky enough to witness fertilisation, and to secure preparations showing 
the two gametic nuclei within the newly-fertilised oospheres. 
Some writers have discounted the accounts of the gametophytes on the 
ground that the latter had only been obtained in cultures. The objection 
is no longer valid, for Ikari® claims, in the case of Laminaria religiosa, to 
have seen the same structures in the natural habitat, and the writer has 
discovered young Chorda sporophytes connected with gametophytes in the 
sea at Aberystwyth. 
The question of the systematic position of Chorda and Saccorhiza has 
already been touched upon. Both the histology and the mode of repro- 
duction justify the growing tendency to place Chorda with the Laminariacee. 
The difference in the initiation of the sporophyte—the fact that the 
ovum does not emerge, that it is still enclosed in the inner wall, and that 
the mouth of the oogonium remains open!’—seems to indicate that it is not 
so closely related to the other genera as they are to each other. Other 
characters deserve consideration—its peculiar form, the fact that the 
whole surface is covered with sporangia, and, in spite of its energetic 
growth, its annual character. Saccorhiza is, in its internal structure, so 
different from all the other Laminariacee that it should be placed in a 
family by itself. The whole plant is unique. It is true that the mode 
of reproduction closely resembles that of the Laminarias ; in other respects 
it is widely different. The large basal bulb; the provisions for maintaining 
the rigidity of the flat stipe (the twist at the base, the curious furbelows1* 
and the strong, fibre-like cells); the sporangia covering bulb (and spines), 
stipe, and parts of the lamina ; the disappearance of the huge lamina and 
stipe at the close of the summer, and the continuance of spore production 
15 Bot. Mag., Tokyo, 35, 1921. 
16 Toc. cit. 
17 Williams, Ann. Bot., 35, 1921. 
18 Barber, Ann. Bot., 3, 1890. 
NT 
