1. EPIDODENDREA E. 1 95 



for example and Walch \ and can be recognised from their figures. It is 

 entirely covered with elongate-rhomboidal flatly conical cushions which 

 touch one another, and each cushion bears a detachment-scar at its most 

 elevated point. This scar answers to the place of separation of a leaf, 

 the whole cushion to the decurrent leaf-base which has remained on the 

 stem. In the crowded position of the cushions which are everywhere in 

 contact with one another the parastichies are very clearly shown, as in fir- 

 cones, and careful study of them discloses very complicated conditions in 

 the arrangement of the leaves. In the large stem of Lepidodendron Stern - 

 bergii preserved in the Museum at Prague, Max Braun found that the 

 phyllotaxy was $ 2 . Elaborate researches into the phyllotaxies which 

 occur in Lepidodendreae have been made by Naumann 3 and Stur 4 . From 

 these it appears that the complicated succession of many-membered cycles 

 with definite divergences, which are exceptional in fir-cones but are 

 frequent in Lycopodiaceae, are the rule in Lepidodendreae, and that simple 

 spiral arrangement is seldom observed. The latter was found by Stur 5 in 

 Lepidodendron Haidingeri with the divergence f : two-leaved whorls occur 

 in L. Veltheimianum with the divergence |i> and three-leaved whorls in 

 the same species with the divergence //^ : five-leaved whorls with the 

 divergence ^Vs and seven-leaved whorls with the same divergence were 

 ascertained in Ulodendron commutatum. From Stur's original account we 

 may learn how he overcame the difficulty arising from the circumstance, 

 that the entire circumference of the stem is not usually open to examination. 

 Stur 6 has also given an elaborate description of the single cushion in 

 all its details. The lateral angles of its rhombic outline are obtuse and the 

 upper and lower angles are acute, and hence it is seen to be bounded 

 by two lateral sinuous lines. It is separated from the eight adjoining 

 cushions either by broad flat strips, or only by sharp linear furrows. In 

 the latter case the bases of the leaves are in immediate contact with one 

 another, in the former they are divided from one another by narrow por- 

 tions of the smooth surface of the stem. How far this circumstance depends, 

 as Stur thinks, on differences in age, or to what extent it is due to specific 

 distinctions, I would prefer to leave undecided. The specimens with broad 

 intermediate strips are in his opinion younger plants ; by further arching 

 over of the Cushions the interstices between them were depressed and 

 became continually more like furrows, the narrow intermediate strips being 

 more and more covered over and withdrawn from observation. The scar, 

 from which the leaf-blade separated, occupies the highest point in the 

 flatly pyramidal cushion. It varies in size and is transversely rhombic in 



1 Walch (1). a Schimper (1), vol. ii, pt. I, p. 15. 3 Nanmann (1). * Stur (5), p. 236. 



Slur (5), p. 259. * Stur (5), p. 227. 



O 2 



