310 



plants from here the flowers occur on a considerable part of 

 the stalk in the axils of flaccid, presumably submerged leaves 

 as well as on the upper leaves. 



According to Kndth (1898 p. 411) fertilisation takes place 

 by means of the wind. In the pond of the Botanical Gardens, 

 Copenhagen , however, some fruits were formed on the sub- 

 merged shoots, which had flowered though less richly than the 

 "air-shoot", down to 10 cm below the surface of the water. 

 Whether these fruit-bearing, submerged shoots have been less 

 submerged during the period of fertilisation, or whether the 

 conditions of fertilisation are different from what is known, 

 must remain an open question. 



As the flowers are protogynous (Knuth 1. c), it is difficult 

 to determine from the material, which is for the most part 

 dried, whether in some cases, where only pistils can be seen, 

 the stamens are not at all formed, or whether they are not 

 yet developed. Gynodioecy has several limes been observed 

 (Kndth 1. c). Schacht (1850 p. 165) found, that the anthers 

 failed in dry and warm summers; in May he found c? flowers, 

 in July Ç flowers. In the pond of the Botanical Gardens, in the 

 but little sunny summer of 1907, the upper or lower whorls in 

 the flowering part of the stalk of a number of specimens con- 

 sisted wholly or partly of female flowers. It is possible that 

 they occur in greater quantities in sunny summers. Hellenius 

 (1786) says, that H. maritima seems to be always hermaphro- 

 dite; neither Linné nor Lindberg mention the flowers in the 

 synonymous H. tetraphylla. 



Some of the plants were taken with fruit, though the col- 

 lections do not embrace the whole summer. The fruits are 

 however in general empty. Developed fruits were found in 

 plants from Røde Ö on Scoresby Sound, East Greenland 

 ca. 70° N. L. Hartz (1895 p. 148) describes the region here as 

 having the most copious vegetation he had seen in Scoresby Sound. 

 The bottom of the small lake, which lies ca. 185 m above the 



