124 Knud Jessen. 



stris and Rubus chamæmoriis show characters in their leaf- 

 structure which undoubtedly should be regarded as agents 

 serving to prevent excessive transpiration, and yet they 

 grow in sphagnum-hog» as do Ran. Pallasii and Ran. lapo- 

 nicus, the leaves of which I should characterize more 

 closely as mesomorphic-hydrophilous — a fact which 

 indicates that the adaptation of plants is not evidenced 

 solely by morphological conditions. 

 G. In the majority of the species the flowers are fairly con- 

 spicuous, least so in the Alchimilla-species and in Sibbal- 

 dia, but here they are gathered into more or less con- 

 siderable inflorescences; Sorbus has richly flowering co- 

 rymbs, but in the remaining species the flowers are either 

 solitary or gathered into usually few-flowered cymes. 

 Two species have red flowers, viz. Pot. palustris, and Rub. 

 arcticus; the following have white flowers: Pot. trident ata, 

 Dryas, Rub. chamæmoriis, Rub. saxatilis and Sorbus; the rest 

 have yellow petals. All the species undoubtedly produce 

 honey, which is secreted by the inner side of the hypan- 

 thium ; in several species a disk is developed (Pot. triden- 

 tata, Sibbaldia and Alchimilla). A slight perfume has 

 been noted in a few species only. Well-marked hercogamy 

 occurs in only a few of the species; Rubus chamæmoriis 

 is dioecious, Dryas is andro-monoecious and Pot. palustris 

 is highly protandrous. The others are homogamous or 

 have, at the most, a short preliminary unisexual stage. 

 Slight protandry has thus been observed in Pot. tridentata, 

 Pot. maculata, Dryas (some of the hermaphrodite flowers) 

 and Rubus arcticus, while Pot. anserina, Pot. emarginata(?), 

 Dryas (some of the hermaphrodite flowers) and Sorbus 

 are slightly proterogynous. It must be assumed that 

 self-pollination can take place in all species except in the 

 Alchimillas, Rub. chamæmorus and Pot. palustris. There 

 are only very sparing notes to hand as regards direct 



