216 E. C. Andrews — The Geological History of the 



more or less withered stock of the tribe, namely, the great sub- 

 tribe, Gbaaphalieee. 



Gnaphalium, close to Helichrysum, is a cosmopolitan, and 

 favors the tropics. The Helichrysum, or everlasting, group 

 favors waste stony and sandy localities outside the cold regions. 

 A study of the Australian types such as Helichrysum and Cas- 

 sia hi suggests that the early forms were trees favoring open 

 places. A study also of the distribution of the Helichryseae 

 suggests that they are a branch of Gnaphalieac which arose as 

 warmth-loving types during the first great differentiation of 

 climate and which spread thence to Australia, Africa, and New 

 Zealand. As time progressed, and as the severe conditions of 

 the middle, later, and post-Tertiary approached, they took 

 refuge, in great measure, on the sandy barren wastes of Aus- 

 tralia and South Africa, soils which had also been the salva- 

 tion of the Proteacese, the Ericaceae, Epacridacea?, Legumi- 

 nosae, Myrtaceae, and many other families. In proportion as 

 the arborescent form was discarded, and the herbaceous habit 

 adopted, so did the types succeed in life. In the northern hemi- 

 sphere they were not as successful as in the southern because, 

 unlike Senecio and Aster, they were not adapted to the cold cli- 

 mate so much as to the drier, sandy and stony wastes in warmer 

 climates. The great display of Helichrysum and Helipterum 

 both in South Africa and temperate Australia does not, there- 

 fore, demand the existence of a direct land connection between 

 the two so much as it demands an old land connection between 

 them by way of the tropical regions, the sandy barren wastes in 

 each of the southern areas acting as a place of refuge to these 

 types. 



(4) The Ericaceae and the Epacridacece. 



These related families appear to have had two, if not more, 

 distinct periods of revival, the one before the great isolation 

 of the larger land blocks, the other during the great differentia- 

 tion of climate culminating in the Glacial Period. 



Both belong to the Sympetalse. The Ericaceae possess 8 or 

 10 stamens, all free, the anthers generally opening in pores 

 and possessing appendages in many instances, while the Epacri- 

 daceae have 5 stamens generally attached to the corolla tube, 

 the anthers are only 1 celled, and they open in longitudinal 

 slits, although a more primitive type (Prionotes), has its 

 anthers two-celled. The venation is very peculiar, consisting 

 of parallel nerves, very suggestive of monocotyledonous forms, 

 while the Ericaceae possess penniveined leaves. 



