Australian Flowering Plants. 225 



to Australia during the earlier differentiation of climate and 

 that it was killed off at a later period in Australia. Quercus 

 also may have travelled south during the earlier period, but its 

 distribution suggests that it belongs to the later period of 

 development. So also Salix appears to belong to the second 

 period. It seems permissible, however, to infer that Alnus, 

 Salix, Quercus, and some allied types, are to be referred to 

 the period of development of Astragalus, TJlex, Lathyrus, Vicia, 

 Lupinus, and Carduus, namely, one after the isolation of 

 Australia and New Zealand from the world proper. 



The absence of these types from South Africa may be 

 explained as being due to the lack there of cool, to cold, and 

 well-watered country such as occurs in Southern Chili, South- 

 east Australia and New Zealand. Before any family adapted 

 to the xerophytic conditions within South Africa had oppor- 

 tunity to develop, the plants with catkins appear to have 

 perished in that region. 



These notes are inserted here merely with the intention of 

 drawing attention to the hitherto unexplained botanical diffi- 

 culties on the assumption of a Tertiary or post-Tertiary land 

 connection between the southern lands and Antarctica. On 

 the other hand the "Cretaceous and Eocene radiation" affords 

 one explanation of this peculiar angiospermous distribution. 



(d) The Northern Hemisphere Problem. 



This is bound up in the general problem of South America 

 and South Africa, and the possible distribution of one family 

 only, namely, Umbelliferse, is discussed, inasmuch as it is 

 typical of the distribution of families such as Crucifera3, the 

 Amentales, Ranunculacea^ Gentianacese, Scrophulariacese, Bor- 

 aginacese, and Stellatse (Lindley). 



(1) The Umbelliferce. 



A study of the distribution and nature of the umbelliferous 

 plants suggests that there have been at least two great dif- 

 ferentiations of climate in the world since the birth of the 

 family. This is especially well seen by a comparison of the 

 Australian and northern hemisphere types. 



The Umbelliferse belong to an order of specialized forms 

 known as the Umbellifiorse containing three families, namely, 

 the Araliacese, Umbelliferse, and Cornacese. The Araliacese 

 are large trees of luxuriant habit, which are found generally 

 in the fertile tropics or subtropics. The Umbelliferse are 

 mainly herbs, with leaves usually highly compound. In a very 



