SEVENTEENTH aND EIGHTEENTH CENTURIES 1 97 



from the fact. It was left to another scientist, Camerarius, to prove the sexu- 

 ality of plants. 



Sexuality of plants 

 It was known of old that in certain plants the individuals are of two differ- 

 ent kinds, both of which must concur before any reproduction by means of 

 fertilization can take place. The classical example of this, known to all the 

 natural philosophers of antiquity, is, as mentioned above, the date-palm, 

 the fruitful specimens of which have been quite correctly called, by the 

 peoples who cultivate them, females, while those that are required for 

 fertilization have been called males. But other plants of the same kind have 

 also been known since ancient times, though many plants that resembled one 

 another, but were differentiated by varying size and development were taken 

 for females and males. A well-known instance of this was that of the two 

 ferns Filix mas and Filix femina, which are still retained as names of species 

 in two different fern-genera. But these ideas mostly belong to popular belief; 

 scientists, both those of the classical period and, on their authority, those 

 of the sixteenth and seventeenth centuries, denied, or at any rate overlooked, 

 the existence of sexuality in plants, owing mostly to the fact that the great 

 majority of plants are hermaphrodites. When no difference can be found in 

 the male and female specimen, what is the use of assuming sexual reproduc- 

 tion? Grew was the first to believe that plants reproduce themselves sex- 

 ually, "like snails" (these are, of course, also hermaphrodites). His opinion 

 in this case, however, was based mostly upon theoretical speculation, and, 

 as a rule, such speculations are, of course, less convincing than direct obser- 

 vation. The scientist who proved the sexuality of plants as the result of 

 convincing experiments was Rudolph Jacob Camerarius (1665-17^1). He 

 belonged to an old scholarly family, known since the Renaissance period, 

 which had originally been called Cammerer, and he worked throughout his 

 life at Tubingen, where he was for many years professor of medicine. He 

 generally recorded the results of his work in small articles, frequently writ- 

 ten, according to the custom of the period, in the form of letters to other 

 scholars. The essay which alone justifies the mention of his name in a history 

 of biology is a "Letter on the Sex of Plants," dated 1694. In this article he 

 gives an exhaustive account of all the ancient authorities' ideas of the re- 

 production of plants and of the parts of flowers; he himself arrives at the 

 conclusion that the pollen is the male, and the ovary is the female, element 

 and discusses in connexion therewith a number of theories on sexuality and 

 fertilization in general, without, however, contributing anything of special 

 value from a theoretical point of view. Of all the greater significance are 

 the experiments by which he proves his theory of the sexual properties of 

 plants. He cultivated for this purpose a fairly large number of both monoe- 

 cious and dioecious plants and found that i^ the male flowers are picked off 



