192 The Science of Life. 



and tobacco smoke; ... he walked for half a day 

 without rest even when an old man; . . . on Sundays 

 he usually conducted botanical excursions which any 

 one might join on payment of two or three groschen. 

 . . . "On these occasions", an old pupil says, "he 

 explained equally well the inscription on a tombstone, 

 the construction of a windmill, the course of the stars, 

 or the structure of a plant . . . the commonest plant 

 became new by what he had to say about it; a hair, 

 a spot, gave him opportunity for questions, ideas, in- 

 vestigations." 



The life-work of Sprengel was expressed in his now 

 famous book The Secret of Nature discovered in the 

 Structure and Fertilization of Flowers (1793), which 

 gives a detailed account of his observations on the 

 flowers around Berlin. He showed that most of the 

 flowers have nectar, and he interpreted the colour as an 

 advertisement of this, suited to catch the insect-eye. 

 By the insects' visits pollination is secured, which is 

 important, since self-pollination is often impossible for 

 various reasons, but especially because of a want of 

 time-keeping (dichogamy) between the stamens and 

 pistil of a given flower. But there is no detail of the 

 flower without its meaning: variously coloured spots 

 serve as honey-guides or pathfinders to the exploring 

 insects, hairs protect the nectar from rain and yet offer 

 no obstacle to desirable visitors, other arrangements 

 secure that the insects are dusted with pollen; such was 

 the tenor of this pioneer's interpretation, all in a manner 

 with which Darwin and his successors have made us 

 familiar. If Sprengel had only discovered the utility 

 of cross-fertilization, which Darwin proved experimen- 

 tally, his work could hardly have been overlooked as it 

 was. 



The Secret of Nature seems to have fallen quite flat, 

 probably because little interest was at that time taken 

 in such inquiries, partly perhaps for extrinsic reasons, 

 such as the unpopularity and unconventionality of the 

 author. At all events, for nearly seventy years after its 

 publication this bionomical classic was unjustly for- 

 gotten. In 1841 it came into Darwin's hands, and 



