18431882] ACCIDENTAL DISPERSION 445 



The strongest argument which I can remember at this instant Letter 339 

 is A. de C., that very widely ranging plants are found as 

 commonly on islands as over continents. It is really pro- 

 voking to me that the immense contrast in proportion of 

 plants in New Zealand and Australia seems to me a strong 

 argument for non-continuous land ; and this does not seem 

 to weigh in the least with you. I wish I could put myself in 

 your frame of mind. In Madeira I find in Wollaston's books 

 a parallel case with your New Zealand case viz., the striking 

 absence of whole genera and orders now common in Europe, 

 and (as I have just been hunting out) common in Europe in 

 Miocene periods. Of course I can offer no explanation why 

 this or that group is absent ; but if the means of introduction 

 have been accidental, then one might expect odd proportions 

 and absences. When we meet, do try and make me see more 

 clearly than I do, your reasons. 



To J. D. Hooker. Letter 340 



Down, Nov. 14* [1858]. 



I am heartily glad to hear that my Lyellian l notes have 

 been of the slightest use to you. I do not think the view 

 is exaggerated. . . . 



Your letter and lists have most deeply interested me. 

 First for less important point, about hermaphrodite trees. 2 

 It is enough to knock me down, yet I can hardly think that 

 British N. America and New Zealand should all have been 

 theoretically right by chance. Have you at Kew any 

 Eucalyptus or Australian Mimosa which sets its seeds? if 

 so, would it be very troublesome to observe when pollen is 

 mature, and whether pollen-tubes enter stigma readily imme- 

 diately that pollen is mature or some little time afterwards ? 

 though if pollen is not mature for some little time after flower 



1 The Copley Medal was given to Sir Charles Lyell in 1858. Mr. 

 Darwin supplied Sir J. D. Hooker, who was on the Council of the Royal 

 Society, with notes for the reasons for the award. See Letter 69. 



3 See Life and Letters, II., p. 89. In the Origin, Ed. I., p. 100, the 

 author quotes Dr. Hooker to the effect that " the rule does not hold 

 in Australia," i.e., that trees are not more generally unisexual than 

 other plants. In the 6th ed., p. 79, Darwin adds, "but if most of the 

 Australian trees are dichogamous, the same result would follow as if 

 they bore flowers with separated sexes." 



