. Bulletin of the British Museum (Natural History), Geology. MATONIA BRAVN1I (GOEPPERT) 301 had indusia I decided this was impossible. Like others I was convinced that P. braunii had naked sori, this being the character that distinguishes Phlebopteris from Matonia. There seemed a grave practical difficulty. There were two groups of well-preserved specimens, P. braunii in the Lower Lias of western Europe and East Greenland in which certain specimens, though a minority, showed naked sori, and the new Yorkshire group in which certain specimens showed indusia when transferred. But most specimens w
. Bulletin of the British Museum (Natural History), Geology. MATONIA BRAVN1I (GOEPPERT) 301 had indusia I decided this was impossible. Like others I was convinced that P. braunii had naked sori, this being the character that distinguishes Phlebopteris from Matonia. There seemed a grave practical difficulty. There were two groups of well-preserved specimens, P. braunii in the Lower Lias of western Europe and East Greenland in which certain specimens, though a minority, showed naked sori, and the new Yorkshire group in which certain specimens showed indusia when transferred. But most specimens were indistinguishable and this applied also to nearly all those figured previously except the ones showing details of sori. It seemed that the groups were generically distinct but could seldom be distinguished and I tried to escape from the difficulty with elaborate Fig. 17 Two pinnules of Matonia braunii, , Scoresby Sound, East Greenland, x 10. Shrinkage after collection caused cracks to form in the indusium between the sporangia and around the placenta. The sporangia contain ripe spores but their annulus is not visible. Later, when I saw Liassic specimens off. braunii in the BM(NH) the difficulty vanished. P. braunii also has an indusium but is apt to lose it. I suggest that collectors selected against specimens with sori concealed by indusia, as I evidently did in Greenland. For example, specimen 15043 from Bayreuth, Bavaria, labelled Laccopteris muensteri, shows the under-surface of many fertile pinnules, some with intact sori, others denuded. In the intact sori the sporangia form vague bulges but do not show their annulus cells and I conclude that this is because they are covered by an indusium. The evidence is not fully convincing because it is possible that this specimen had been coated with varnish which obliterated them, although I see no sign of any such varnish. Equally, specimen , collected by me from the Lower Lias of East Greenland and s
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