. The testimony of the rocks; . have belonged to a marinevegetation notwithstanding. I detected some years ago,in the Trilobite-bearing schists of Girvan, associated vrithgraptolites of the Lower Silurian type, a vegetable organismsomewhat resembling the leaf of one of the pond weeds, —Jin order of plants, some of whose species, such as Zostera,find their proper habitats in salt water. I have placedbeside this specimen a fragment of the same graptolite-bearing rock, across which I have pasted part of a leaf ofZostera marina, the only plant of our Scottish seas whichis furnished with true roots
. The testimony of the rocks; . have belonged to a marinevegetation notwithstanding. I detected some years ago,in the Trilobite-bearing schists of Girvan, associated vrithgraptolites of the Lower Silurian type, a vegetable organismsomewhat resembling the leaf of one of the pond weeds, —Jin order of plants, some of whose species, such as Zostera,find their proper habitats in salt water. I have placedbeside this specimen a fragment of the same graptolite-bearing rock, across which I have pasted part of a leaf ofZostera marina, the only plant of our Scottish seas whichis furnished with true roots, bears real flowers inclosed inherbaceous spathes, and produces a well formed farinaceousseed. It will be seen, that in the few points of comparisonwliich can be instituted between forms so exceedingly sim-ple, the ancient very closely resembles the recent organism. FOSSIL FLORAS OF SCOTLAND. 431 It is not impossible, therefore, that the Silurian vegetablemay have belonged to some tribe of plants allied to Zostura^ Fig. a, SILTJEIAN ORGANISM. h, GRAPTOLITE. C, PORTION OP THELEAF OF ZOSTERA MARINA. and if so, we can easily conceive how the Silurian anthraciteof our country may be altogether of marine origin, andmay yet exhibit in its microscopic tubular fibres vestigesof a vegetation higher than the algae. [It were well, in dealing with the very ancient floras, inwhich equivocal forms occur that might have belonged toeither the land or the sea, to keep in view those curiousplants of the present time, the habitats of which are de-cidedly marine, but which are marked by many of thepeculiarities of the seed-bearing plants of the land. Thesuperiority of Zostera to the common sea weeds of ourcoasts appears to have struck in the north of Scotland eyesvery little practised in such matters, and seems to havegiven rise, in consequence, to a popular myth. Zosteramarina abounds on a series of sand banks, partially 432 ON THE LESS KNOWN uncovered by the larger stream tides, which li
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