276 The Plant World. 



Kryz, in the Zeitschrift fur Pflanzenkrankheiten, describes 

 experirr.ents on the influence of kerosene oil on the development 

 of Datura stramonium and Alisma plantago. He concludes that 

 kerosene renders the soil physically and physiologically dry, 

 resulting in checking the growth of the plant, but that there is 

 no proof of its direct poisonous effect. 



Durand, in "Botanical Exploration of the Congo," states 

 that this region is so vast that the materials thus far accumulated 

 are absolutely insufficient to admit of exact conclusions regarding 

 the distribution of its species. Nevertheless, his statistical re- 

 view, based on studies thus far made (North to the French 

 Congo and Southwest to Angola), is of much interest. The 

 tropical African species number 1,355, and include 390 of wide 

 occurrence in the whole of tropical Africa, ISO that may be desig- 

 nated as South tropical, and 785 as Western tropical. Of these 

 785 species, 109 represent types widely distributed in the whole 

 of western tropical Africa; 491 western and northern t\pes which 

 appear to find on the Congo their limit of m.eridional expansion; 

 185 types of Angola which appear not to pass farther north than 

 the colony of the Congo. If we add to these groups about 105 

 species which inhabit not only the tropical region but also other 

 regions of the dark continent, both north and south, we should 

 have a total of three thousand African species. There are on 

 the Congo 1 7 species which are also found in Belgium and 23 in 

 other parts of Europe. There are also 122 which occur both in 

 Asia and Africa of which 20 widely distributed in Africa are 

 unknown beyond Arabia. Mention may also be made of 61 

 species scattered throughout the tropical regions of the Old 

 World, 55 species found in all tropical regions wdth the excep- 

 tion of AustraHa, and 120 species widely distributed in the tropi- 

 cal regions of both hemispheres; to this last group belong 43 

 cultivated species, the origin of which is unknown. There are also 

 84 species which occur on the Congo, in the Antilles, and in 

 Central or South America, but 20 of these are introduced species. 



As reported by Paulsen in the Botanisches Centralblatt, an 

 attempt has been made by Raunkiaer to place the treatment of 

 plant formations, hitherto largely subjective, upon a solid founda- 



