124 



2 Groups consisting of a number of polymorphous species, with a 

 disposition to hybridism. These — the neotypical — are the 

 youngest, and are still in the full process of development. 



To the former category, which consists of ligneous species with 

 pinnate, arliculate leaves and hairy fruits, belongs P. fruticosa. In 

 \Volf's natural system, wich is grounded on the character of the 

 carpels, the species is reckoned amongst the Sectio Trichocarpce 

 (with hairy fruits), Subsectio RhopalosUjkv (with club-shaped style), 

 and Grex Fruticoscv (pure bush-nature, articulated leaves, fruit 

 closely covered with hairs). 



Geographical distribution: In Asia: Siberia, Central and 

 Eastern Asia, Kamtschatka, the Islands of the Behrings Sea, Japan, 

 Corea, Mandchuria, China, the Himalaya-lands, the Caucasus, Ar- 

 menia. In Europé: South Russia, the Ural, Estland, Courland, 

 (Livland?), Öland, Gotland, the north of England, Ireland, the 

 Pyrenees, the Maritime Alps. In North America: In the east, 

 from Labrador to New Jersey; in the west, from Alaska to Cali- 

 fornia, and in the mountains of New Mexico and Arizona. 



In Öland, P. fruticosa occurs only on the southern „alfvar , 

 growing in colonies. On the ,, alfvar two kinds of soil can be 

 distinguished: 1) Exlensive slabs of limestone, either naked, or cov- 

 ered with a thin layer of earth, and with open vegetation. 2) 

 Somewhat deeper earth, with close vegetation. P. fruticosa grows 

 in both localities; in the former in the cracks between the stones 

 and, in the latter in places, where the ground is knolly, damp, and 

 somewhat stony (see the fig." 1 and 2). It is most common in the 

 localities last-mentioned. The places where it occurs in Gotland 

 resemble pretty much the Öland habitat of the species. 



In both islands, P. fruticosa occurs together with a relatively 

 large percentage of glacial-, sub-glacial- and oak-growths, and above 

 the limits of the ancient Ancylus Lake, although on Öland it bas 

 since spread below the same. Apparently, the species immigrated 

 to Öland and Gotland across the Baltic Provinces, during the pe- 

 riod which, in Sernander's terminology, is called the ,,arctic . 



THE VARIATION IN THE VEGETATIVE SYSTEM. 



P. fruticosa grows both as single plants and also in groups. The 

 height of the bushes varies between 10 centimetres (3,9 inches) up 

 to more than 1 — V /o metre (circa 39 — 59 inches). The tallest spe- 



