315 



A strikingly large number of plants are delicate and the 

 lobes of the leaves are fine as hairs, as Schenck (1886 a p. 23> 

 mentions in Myriophyllums from very still and small pools. 



Abromeit (1899 p. 12) describes specimens from Ikerasak 

 (Umanak region, 70°30' N. L., West Greenland), taken by Vanhoffen 

 1899; the leaves have a broad central part and few, but broad 

 lateral lobes or these are absent. A plant of the same material 

 in our possession bears such leaves with lateral lobes on a 

 part of a shoot, whilst the rest of the plant 

 looks like the ordinary M. spicatum (fig. 8). 

 The vein of the main part has lateral veins, 

 its tip is bent like a cap but has no marks 

 from the usually occurring and deciduous, 

 trichome-like appendages, which however 

 the lateral lobes show. The leaves examined 

 have no slomata. Abromeit mentions some 

 shield-shaped hairs, and he considers 

 this form to be near to M. spicatum ß 

 heterophyllum Petermann, whose original 

 description has not been accessible to me Ч 

 Such hairs I have not seen, possibly because 

 the available material was very scarce. Whether 

 these leaves are formed in the air or under 

 other special outer conditions is not known. 



The adventitious roots have a distinct 

 ectodermis. Their woody parts is extremely feebly developed, 

 often only one or 2 vessels in each of the rays, the number 

 of which varies from 2 to 4 within the same order of root, the 

 first one on the same plant. On Schenck's figures (1886 b) a 

 root of M. spic. is given as pentarch, whilst its root-branch 

 only has two vessels on the whole; the root of the land-form 

 0Ï M. a. is tetrarch. Here as in most of the cases referring 



Fig. 8. Myriophyl- 



lum spicatum L. (X 



ea. 5). 



Leaf of a lateral shoot. 



(Ikerasak, Umanak, West 



Greenland). Lateral lobes 



not finished. 



^ According to Koch (1892 p. 865) ß) heterophyllum has "die obersten 

 Blätter aufgetaucht (schwimmend) lanzettlinealisch, ganz". 



