364 



DARWINISM 



CHAP. 



pared with the enormous areas of sea-bottom, over which the 

 atmospheric dust must have been scattered, render it in the 

 highest degree improbable that the maximum limit either of 

 size of particles, or of distance from land has been reached. 



Let us, however, assume that the quartz grains, found by 

 Mr. Murray in the deep-sea ooze 700 miles from land, give us 

 the extreme limit of the power of the atmosphere as a carrier 

 of solid particles, and let us compare with these the weights 

 of some seeds. From a small collection of the seeds of thirty 



No. 



Species. 



Approximate 

 No. of Seeds 

 in one Grain. 



Approximate 

 Dimensions. 



Remarks. 









in. in. in. 





1 



Draba verna 



1,800 



inr x tV x Tib 



Oval, flat. 



2 



Hypericum perforatum 



520 



1 v 1 



■sir x "sir 



Cylindrical. 



3 



Astilbe rivularis . 



4,500 



fV X TC7 



Elongate, flat, tailed, wavy. 



4 



Saxifraga coriophylla . 



750 



T0-X7V 



Surface rough, adhere to the 

 dry capsules. 



5 



(Enothera rosea . 



640 



1 v 5 



TIT x w 



Ovate. 



6 



Hypericum hirsutum . 



700 



TO" X TTT 



Cylindrical, rough. 



7 



Mimulus luteus . 



2,900 



1 v 1 



Oval, minute. 



8 



Penthorum sedoides . 



8,000* 



TV X T5~D" 



Flattened, very minute. 



9 



Sagina procumbens 



12,000* 



T21T 



Sub-triangular, flat. 



10 



Orchis maculata 



15,000* 





Margined, flat, very minute. 



11 



Gentiana purpurea 



35 



1 



Wavy, rough, with this cori- 

 aceous margins. 



12 



Silene alpina 





A' 



Flat, with fringed margins. 



13 



Adenophora communis 





To" X TT 



Very thin, wavy, light. 





Quartz grains 



25,000 



vlv 



Deep sea . . 700 miles. 





Do. 



200,000 



TVTf 



Genoa . . . 600 miles. 



species of herbaceous plants sent me from Kew, those in the 

 above table were selected, and small portions of eight of 

 them carefully weighed in a chemical balance. 1 By counting 

 these portions I was able to estimate the number of seeds 

 weighing one grain. The three very minute species, whose 

 numbers are marked with an asterisk (*), were estimated by 

 the comparison of their sizes with those of the smaller weighed 

 seeds. 



If now we compare the seeds with the quartz grains, we 



1 I am indebted to Professor R. Meldola of the Finsbury Technical Institute, 

 and Rev. T. D. Titmas of Charterhouse for furnishing me with the weights 

 required. 



