80 
stone, in the Romney Marshes; but, owing to the banking-up 
of the creek where it was found, it has since disappeared. The 
latest addition to the area was made by the discovery of some 
colonies in the estuaries of the Rivers Saire and Yire, in the 
Peninsula of Cherbourg, about ioo miles due South of the Isle of 
Wight. 
The dispersal of the seeds is, no doubt, mainly due to the 
action of the water into which the spikelets fall when detached. 
Once in the water they would float about until waterlogged. Some 
would sink in the neighbourhood of the parent plant, but many 
would be carried by the tides or currents either to the shore or 
along the shore, or even across estuaries and straits before they 
sink, and, under favourable conditions, start, in due course, new 
colonies. Birds may also have been dispersing agents, although 
it is doubtful that they ever played an important role in that 
respect, except in so far as they may have carried spikelets to 
localities which, by the ordinary action of tides and currents, could 
not be reached. The same may be said of man and his shipping. 
But apart from seeds, dispersal may also take place through 
detached pieces of stolons, such as are found floating or cast 
out on the shore after heavy gales. 
Various theories have been advanced to explain the first 
appearance of the grass in the English flora. The most plausible 
would seem to be that it was due to accidental introduction from 
a foreign country; but our present knowledge of the genus and 
its distribution does not support it. Another suggestion is that 
Townsend’s grass arose as a sport or mutation from Spartina 
stricta , which formerly used to grow on the shores of Southamp¬ 
ton Water. Spartina stricta is, however, a singularly uniform 
and conservative species throughout, its area, rather receding 
than advancing, and slow in adapting itself to changed conditions. 
It is evidently not the material from which one might expect 
sports or mutations to spring, so distinct and vigorous as Towns¬ 
end's grass. 
There is, however, a third theory which is more 
plausible. According to it, Townsend’s Spartina arose from 
a cross between S. alterniflora and S. stricta. S. stricta does 
not at present occur in the neighbourhood of Southampton or 
in Southampton Water; but we know for certain that it did so 
not very long ago. S. alterniflora is common in the Itchen River 
and also found in various places at the head and on both sides 
of Southampton Water. There was, no doubt, sufficient 
opportunity for the two species to hybridise. Unfortunately it 
has not been possible so far to produce artificial hybrids of S. 
alterniflora and 5 . stricta. The evidence in favour of this theory 
is, therefore, necessarily circumstantial. It rests partly on the 
structure and the general behaviour of the grass, and partly on 
the occurrence of a natural hybrid between the same two parents 
in another part of the world and its extreme similarity to Towns¬ 
end’s grass. As to structural characters, there is no doubt that 
