K.—BOTANY. 191 
generation of Padina, and Mr. Carter, one of my assistants, has a paper 
on the same subject awaiting publication. All the results are confirmatory 
_ of the existence of meiosis in the tetraspore mother cell in the Dictyotacee. 
_ Furthermore, most of us know that Hoyt, for Dictyota, and Wolfe, for 
_ Padina, cultivated, in the sea, plantlets from tetraspores, and from fertilised 
_ eggs started on oyster shells ; and in this way they obtained confirmation 
_ of the existence of alternation. But there are certain facts that make it ex- 
tremely difficult to understand how the succession of plants is maintained. 
- Both Taonia and Padina are, on our coasts, almost solely tetrasporic. I 
have not collected a gamete-bearing plant of either for years! From fairly 
deep water in Cardigan Bay, big, tangled clumps of thread-like f. intricata 
of Dictyota can be dragged: it is invariably asexual. In dredging for 
 Cutleria in the estuary of the Yealm, quantities of very broad Dictyota 
often came up: it never bore reproductive organs of any sort. In the 
! three first cases the problem is, what becomes of the myriad tetraspores 
that are shed; and, in the absence of sexual plants, where do the 
4 abundant tetraspore plants come from? Have the plants any contrivance 
for perennation? If so, the tetraspores must have lost their function. 
If not, there must be some cytological changes as yet undiscovered. 
In the writer’s Dictyota work it was proved that the supposed par- 
_ thenogenesis reported by earlier observers consisted only of a few apparent 
segmentations. A cytological examination showed that the nuclear 
figures were very irregularly multipolar ; and as a result the chromosomes 
ee irregularly distributed, ultimately forming nests of nuclei. This made 
it evident why under these conditions normal segmentation could not go 
on. Wolfe has shown by cultural methods that ‘ unfertilised eggs divide 
freely, producing a cell-body of varying size, but which invariably fails 
to mature.’ It would be interesting to find out in this case also how the 
nuclei behave. It is instructive to note that, in the Cutleriaceze, both 
‘parthenogenesis and apogamy can occur. In the Dictyotacee the 
capacity for producing plants from unfertilised ova has been lost, except 
for a few initial divisions. In experiments on unfertilised oospheres of 
Fucus, a few showed projections suggestive of incipient rhizoids, but the 
nuclei never showed signs of dividing, and the oospheres never even 
acquired proper walls. This takes no account of experiments, such 
as Overton’s, in artificial parthenogenesis. 
The great importance attaching to Sauvageau’s discovery of the 
gametophytes of Saccorhiza has already been mentioned. The young 
sporophytes of Laminaria, Chorda and Alaria had already been identified, 
but the gametophytes from which they arose were called protonemata, 
while the very small-celled male gametophytes in the cultures were 
regarded as intruding Alge. There was a growing suspicion as to their 
e nature, but the proof obtained by Sauvageau was a very unexpected 
one, exhibiting a curious peculiarity of Saccorhiza. Many of the 
“sporangia do not liberate their spores: the wall swells greatly and the 
‘Spores germinate into the two kinds of gametophytes while still enclosed. 
I have been able to verify this for myself. One wonders whether this 
curious behaviour obtains in the sea; and, if it does, whether it is of 
advantage to the plant. Yendo’s' account of Phyllitis shows some 
distinctive features. While filamentous gametophytes are formed in the 
14 Bot. Mag., Tokyo, 33, 1919. 
