288 



Si ratiotes aloides and Hydrocharis morsus rance, both of which are com- 

 mon in Denmark al the present day, are nol found either as inssil in our 

 postglacial I »» » ^ ^ . Whilst at the present daj they seem to develop ripe fruits 

 extremelj seldom, numerous seeds ol them are found in our interglacial bogs; 

 some of them are flgured on PI. IX. <> n pp. 126 l'JT is mentioned the diffe- 

 rence between the smooth and slender Stratiotes seed from the interglacial 

 deposits ;hkI the more sculptured seed found in the amber pin beds. 



Ol special interesl is the occurrence ol the two genera Brasenia and 

 Dulichium which no longer grov in Europe. 



Brasenia, which al the presenl daj li\cs in North America, Easl Asia, 

 Africa and Australia, and which frequentlj occurs in the tertiary and inter- 

 glacial layers of Europe was found bj me in the bog ori Tuesbol Common; 

 in L907 l found il together with Picea, Carpinus, Dulichium and the usual 

 interglacial planl association in the interglacial peal on Sylt. 



Dulichium spaihaceum Pers., the only species of the genus Dulichium 

 (CyperaceæJ 1 i \ i n.u. at the present time, is widely distributed over the whole 

 ni eastern North America, from Canada, New Poundland and Nova Scotia 

 in the north to the tropical Florida in the south; towards the wesl il reaches 

 to Minnesota and Texas. It is a swamp and water plant, which grows socially 

 on the banks of rivers and lakes, in damp bogs or right out in the water. 

 The species w;is not known as fossil before I found it in l<S!)<s in the bogsal 

 Tuesbøl, Lervad and Holland Sogaard, bul it has later been found (according 

 to w ritten communication) by Beyle in the interglacial 6og ;il Lauenburg 

 (Kuhgrund), and in l ( .»i>7 1 found il in the interglacial peat :it Westerland on 

 Sylt. A related species. I), vespiforme, has in 1908 been described by Cl. & 

 El. Reid Ironi the preglacial clay ;il Tegelen. The species has died out in 

 Europe in the interglacial period and is indeed like Brasenia an old tertiary 

 circumpolar species. 



In addition to the interglacial characteristic fossils mentioned practically 

 all mir present-day forest trees and numerous bushes and vegetables occur 

 in the deposits dealt with liere; of these however I shall liere only mention 

 the ha/.el (Corylus avellanaj. The very distinctive fruits of tids species have 

 been collected in sufficiently large number to permit of conclusions being 

 drawn with regard to their power of variation in the interglacial period. In 

 his Monograph: Hasselen i Sverige (1902), Gunnar Andersson distinguishes 

 between three forms of hazel nuts: f. silvestris, f. ovata and /'. oblonga, the 

 liist of which is by far the most common and the last the rarest both at the 

 present time and in the postglacial bogs in Sweden. On pi. XIII I have 

 figured 25 nuts (drawn by means of the prism) from our interglacial bogs, 

 and as will be seen all the three types mentioned are represented amongst 

 them. In the Danish interglacial layers, even in one and the same locality 

 (Ejstrup, Brorup), all the forms are found and under the same conditions as 

 at the presenl dav: /'. silvestris the most common, /'. oblonga the rarest. Il 

 will likewise be noticed, that within each single main form variations with 

 pointed tip and others with pointed, more or less pyramidal hase were also 

 found in the interglacial boas. 



that Picea and Carpinus have wandered from the south to Southern Sweden, 

 and tlmt these species shortly atter their postglacial appearance round the 

 south-western pari of the Baltic have again been driven out. 



Until further information is to hånd regarding the conditions of discovery, 

 it will be difficull to estimate the significance of these linds. 



