304 THE .TOUR^^AL OF BOTANY 



explained b}^ tliis psculiarity, that it tends to die out of pasture land 

 when it is not pulled out of the ground. Whenever it is pulled out 

 of the ground and the surface-soil is thus disturbed, fresh seedlings 

 spring up. I am informed tliat in the Wairarapa district some 

 farmers have expended as much as £150 a year in their endeavours 

 to clear the land of foxglove by pulling it out. Others who have 

 elected to leave it have been fined fifty shillings for a breach of the 

 Noxious Weeds Act, and their land has become nearly clean by the 

 plants dying out of the pastures." 



Mr. Thomson seems doubtful as to the accuracy of the " legend " 

 of the introduction of the Dock {Riunex ohtusijfolius), which has 

 been a " noxious weed " from an early period. Darwin, however, 

 mentioned it in 1835, and Colenso in 1837 visited at Poverty Bay 

 "some young plants the natives had raised from seed, fenced in and 

 tabooed, believing them to be tobacco," under which name they had 

 purchased the seed. It may be noted that Sheep's Sorrel {B. Aceto- 

 sella) really deserves its name, as, although an abundant weed, it 

 ** is mostly kept down by sheep wherever they graze freely." 



There is an interesting chapter on the " Alteration in the Flora 

 since the European Occupation " : no instance can be recorded of 

 any species which has been exterminated as a consequence, but local 

 extermination has taken place, and of this several instances are given : 

 Lepidium oleraceum Forst., for example, originallv discovered by 

 Banks and Solander during Cook's first voyage, and then so abundant 

 that " boat-loads of it were collected and used as an antiscorbutic," is 

 now extinct in several of the localities visited and rare in others ; " its 

 disappearance is due to cattle and sheep, which greedily eat it down 

 in any locality they can reach." This chapter contains a valuable 

 section on the inter-relation of the native and introduced flom ; 

 Mr. Thomson finds " little evidence in support of the opinion that a 

 considerable proportion of the native flora will become extinct," 

 and is " inclined to believe that the struggle between the naturalised 

 and the native floras will result in a limitation of the range of the 

 native species rather than in their actual extermination." The 

 chapter on Legislation contains the schedules of " noxious weeds," 

 to which reference has already been made. 



The volume, which is in every respect a valuable and interesting 

 piece of work, concludes with a full bibliography, an index of authori- 

 ties, and one of animals and plants, each of them admirably done. 



Die Veqetation clerErde. Die Pflanzenwelt Afrikas. Yon A. Exgler. 

 III. Band, 1 Heft, rait 401 Textfiguren, pp. 869, 1915; 2 Heft, 

 pp. 878, mit 338 Textfiguren, 1921. 33 & 340 Marks. Engel- 

 mann, Leipzig. 



These important volumes are devoted to a systematic treatment 

 of the Flora of Africa, especially of the tropical region, and form a 

 valuable contribution to our knowledge of the subject. That great 

 advances have been made in recent years may easily be seen by 

 taking almost any genus, especially of Polypetalae, and noting the 



