THE FLOWER 227 



by the fact that, apart from the very lowest repre- 

 sentatives of the vegetable kingdom which stand, so 

 to speak, on the threshold of the organic world, we do 

 not know a single vegetable group that maintains its 

 existence exclusively by means of a vegetative process, 

 by asexual reproduction as it is generally called ; not 

 one that does not also go through the process of sexual 

 reproduction. 



Let us see under what form this phenomenon takes 

 place in the vegetable kingdom. 



At first, the existence of two sexes was noticed only 

 in some plants, mainly in those that had flowers ; hence 

 the name of Phanerogams given to them by Linnaeus 

 in the eighteenth century in contradistinction to the 

 Cryptogams. To-day the name Cryptogam has lost its 

 meaning, because phenomena of sexual reproduction 

 have been discovered in all classes of plants, with the 

 exception of the very simplest organisms, where it 

 probably does not exist. 



The idea that this process must take place in the 

 flower, and that the fruit and seed, i.e. a young 

 embryo-plant, are the result of this process, ori- 

 ginated long ago ; but as a definite scientific theory 

 it has not more than two centuries of history behind 

 it. 



The idea must have been suggested by such plants as 

 have two kinds of flowers distributed on different 

 individuals. Such are many trees, e.g. the willow, the 

 aspen, the juniper, and also hemp. All these plants 

 produce two kinds of flowers : those that bear the fruit 

 and the seed, and those that possess only stamens, which 

 do not transform themselves into fruit, but are necessary 

 in that they contribute to the formation of fruit in other 

 flowers. The first plant which attracted man's attention 

 in this connexion was probably the date palm. At all 

 events we read that people in the markets of Babylon 

 and the Arabs of later days used to sell the male flowers 



