Over a South Atlantic Continent 437 



sicaceae (Cruciferae) called the Thelypodieae. It is made 

 up of the genus Nothothlaspi with three N. Zealand species, 

 of Decaptera with one, Hexaptera with six, Menonvillea 

 with four, and Cremolohiis with eight species, all of which 

 are mainly S. to N. Chilean, though some occur eastward 

 into Argentina, and others northward into Peru and W 

 Grenada. It consists also of the genus Thelypodium native 

 from Mexico to Oregon; of Streptanthus found from 

 Mexico to Arkansas; of Caulanthiis from California to 

 Utah; of Stanley a from California to Missouri; and of 

 Warea in Florida. A decided distributional continuity and 

 community of descent is therefore indicated here, that ex- 

 tends from central N. America to West Patagonia, thence 

 across the southern hemisphere to the Crozets, Kerguelen 

 and N, Zealand. 



The caryophyllous plant Colohanthns qiiitensis extends 

 from the Mexican Andes south to Cape Horn and Fuegia, 

 thence across the southern ocean to Amsterdam Islands, to 

 Kerguelen and Heard's Islands as C. kerguelensis, and 

 again to the mountains of N. Zealand and Tasmania, where 

 it has split up into two closely related types C. qiiitensis and 

 C. billardieri. The continuous line of distribution then, 

 followed by this one species, is about 14000 miles, while 

 throughout it remains a subalpine plant. The question 

 then may pertinently be asked here, though the answer will 

 be deferred till later: Did the species arise in Patagonia, 

 and then spread northward along the Andes, as well as 

 eastward to N. Zealand, or did it originate in the former 

 or the latter area? 



The tiliaceous genus Aristotelia includes only five spe- 

 cies that closely resemble each other. One is found in 

 Chile, two occur in N. Zealand, and two in Tasmania- 

 Australia. The small spreading rosaceous genus of the 

 Southern Hemisphere Acaena has three nearly related spe- 

 cies that extend from Chile through Fuegia and the Falk- 

 land Islands eastward to Tristan da Cunha, the Marion, 

 Crozet, and Kerguelen Islands, thence to the Macquarie, 

 Auckland, and Campbell Islands, ultimately reaching Aus- 

 tralia, N. Zealand, and Kermadec Islands. This indicates 

 a distributional line of at least 13,000 miles. 



