LINNAEUS 71 



be homologous. The homology of appendicular organs is 

 suggested in the phrase "principium florum et foliorum 

 idem est," and he developed his ideas in two memoirs, 

 Prolepsis Plantarum (1760-63) ; only homologous parts, 

 he said, can change into one another ; " the liver cannot 

 become the heart, nor the heart the stomach." 



In 1751 Linnaeus published his famous Philosophia 

 Botanica a work of the greatest importance ; and in 

 the previous year he constructed his floral clock an 

 arrangement of flowers opening and closing with regular 

 periodicity ; and he described the somnus plantarum, 

 or the nocturnal changes of positions in flowers and 

 leaves. 



With all his ceaseless toil, impetuosity, and hardships, 

 he was always enthusiastic in his studies and researches. 

 In the words of Ovid : " Scribentem juvat ipse favor 

 minuitque laborem ; cumque suo crescens pectore fervet 

 opus." 



Owing to the financial difficulties of Clifibrt, Linnaeus 

 was obliged to leave the beautiful and historic gardens of 

 Hartecamp; but shortly afterwards he obtained employ- 

 ment in the botanical gardens at Leyden. While there 

 he published two other works, which greatly enhanced 

 his reputation. 



At this period in his' career, the Government of the 

 Dutch Eepublic desired to send him on a botanical ex- 

 pedition to South Africa, and they promised to give him 



