part 2] review of pliocene floras. 155 



in the Castle-Eden deposit it formed seven-tenths of the whole 

 flora, and nearly half of this was exterminated. 



The generalization of these facts shown in the curve, makes 

 it ajppear that those elements of the incoming flora which entered 

 earlier were destined to ultimate extirpation in a much greater 

 degree than those which entered later, though for a time they 

 were able to maintain their position. The percentage of the 

 exterminated element steadily increased, until, during the Lower 

 Pliocene and beginning of the Middle Pliocene age, it maintained 

 a fairly-even proportion of about one-third of the whole flora ; 

 after which period it gradually declined. 



The fact that this exotic element of the incoming flora did gain 

 a considerable footing, means that, although the West Euro- 

 pean flora was rather rapidly losing its Chinese-North 

 American character through Miocene and early Pliocene 

 times, yet it was still almost entirely an exotic flora. 



IV. Conclusions. 



Such are the deductions to which the study of Pliocene seeds 

 has led. In conclusion, I would suggest that imperfect though 

 these curves may be, resting as they do upon my own imperfect 

 knowledge and judgment, they nevertheless point to the perfect, 

 the absolute, curve, which shall trace the true course of events. 

 They show that by the application of graphic methods to paleo- 

 botany it should be possible to arrive at broad and accurate 

 generalizations, which may not only be a help to present methods 

 of research, but may even indicate new fields for investigation. 



But if such work is to he done, it must rest upon the gathered 

 knowledge of many workers. As yet it is but in its infancy; of 

 this no one can he more aware than myself. If, however, fossil- 

 seeds are to be studied, and 1 hope that I have made good the claim 

 that they should be studied, both by geologists and by botanists, 

 then we must have seed-collections, so arranged and displayed that 

 they can readily be seen and examined microscopically. For it is 

 not with seeds as with flowers : these have been described and 

 classified, and can be traced, at least in the earlier stages of the 

 determination, by reference to books. Seeds and endocarps must 

 be sought for by the eye. If you cannot see them — what then ? 

 A pea in its pod, or a stone in its berry, for any possibility of 

 comparison, might almost as well be under lock and key. 



I. know that in these days of stress it may be impossible to carry 

 out this work, but I hope that in the future the time may come 

 when it can be taken in hand. 



