8 ARKIV FÖR BOTANIK. BAND 17. N:0 1. 



the margin; and if this is also the case in the fertile pinnae 

 — which cannot be seen — it is clear that the course of the 

 veins and the sori cannot coincide. In most places where 

 both sporangia and veins can be examined the sori are placed 

 not over the secondary veins but between them. This is shown, 

 for instance, in pi. 1, figs. 7 — 10. In the places here figured 

 the sporangia have been partly removed, and the veins thus 

 exposed. The veins do not correspond to the median line 

 of the sorus but to the border line between two sori. In other 

 cases the relation is not so clear, and, on the whole, the relation 

 between the sori and the veins is somewhat irregular. The 

 sori, for instance, do not follow the curve of the veins as these 

 bend downwards to join the midrib, but continue straight 

 in the same direction as nearer the margin. The large sporangia 

 no doubt require an abundant vascular supply, but this seems 

 to be effected by smaller strands which cannot be seen in the 

 specimen. The relation between the sori and the secondary 

 veins as here described is not what would be expected, but 

 somewhat similar conditions were found on an examination 

 of a couple of specimens of typical Danaeopsis marantacea. 



PL 2, fig. 27, is a photograph — about thrice the natural 

 size — of a specimen of Danaeopsis marantacea from Neue 

 Welt near Basel. The photograph gives an idea of the dense 

 irregular nature of the venation. The veins are more nu- 

 merous than the sori, and they are not strictly parallel, as are 

 the sori, but join, and possibly cross, each other in many places. 

 Moreover the veins are of varying thickness. In pi. 2, fig. 29 

 at a and in figs, 28 and 30, it would appear as if the thicker 

 veins corresponded to the borders between the sori, as in the 

 Scanian D. fecunda described above, while in each case a 

 narrower vein corresponds to the median line of the sorus. 

 In other cases, however, the relation is quite irregular. At 

 any rate it is evident that the venation is much denser in the 

 fertile pinna than in sterile ones — as is only natural in regard 

 to the great number and size of the sporangia. In addition 

 to the ordinary veins of the sterile pinnae there is thus in the 

 fertile pinna a set of irregular and probably anastomosing 

 finer nerves suppljang the sporangia. It is possible that the 

 veins of different thickness are at different levels, the thicker 

 ones being more deeply embedded in the parenchyma than 

 the finer ones supplying the sporangia. 



