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new thalli from persistent bases has already been remarked ; 
there exists also the possibility of regeneration from 
small detached portions of fronds—fragments of small 
size but still endowed with sufficient vitality and vigour 
to enable them to re-attach themselves to the substratum 
and produce a whole new thallus. In the autumn large 
masses of plants become torn from their hold and pounded 
into fragments, many of which remain alive for days, 
and during their diurnal pilgrimage with the tide up 
and down the shore, may eventually find harbourage in 
quiet water or lodgment on tiny crevices, on the surface 
of shells or become entangled among the thalli of more 
resistant algae. The relics very soon put out attachment 
organs, anchor themselves to the substratum and so 
begin a new phase of existence in a locality perhaps far 
removed from that in which their first youth was spent. 
Regeneration from floating fragments thus plays a part, 
though perhaps a minor one, in maintaining continuity of 
algal vegetation on the shore. It has been observed that 
genera and species employing this method most successfully 
are those whose attachment organs take the form of 
rhizoidal outgrowths from superficial cells. Among such 
plants are many of the common species of Polysiphonia, 
Ceramium and. Callithamnion. 
A remarkable illustration of the points just raised is 
provided by the study of the “ limpet island ” flora of the 
limestone flats of Port St. Mary. Here saucer- shaped 
pools varying in depth from a few inches to a foot or two 
carry a fairly rich summer vegetation. Underlying the 
plant community is a carpet of Lithophyllum Lenormandt 
(Plate III) which forms in the upper pools a conspicuous 
covering not unlike a very thick and somewhat lumpy coat 
of pinkish white enamel. Round the edges of this floor 
covering and wherever the substratum or the Lithophyllum 
surface gives ready anchorage arise tufts of a very stunted 
