THE PROBLEM 37 



bination of tissue-systems in the stem of a tropical 

 climber. 



Yet, geologically speaking, the Angiosperms 

 are a modern class of plants. At the time 

 when our coal-forests spread so widely over 

 the world they were, for all we know, not in 

 existence; in fact, not a trace of them is found 

 for many ages later; it is high up in the Second- 

 ary rocks that the first Angiosperms appear. 

 Thus, so far as we can judge, their whole course 

 of evolution lay within a period fully open to 

 investigation by the palaeontologist, and belonged 

 indeed to quite the later part of the fossil record. 

 The question, what was the origin of this great 

 modern class of plants, which has prevailed over 

 all competitors, is evidently of fascinating interest, 

 and should not be of hopeless difficulty; yet 

 the problem has always been the great puzzle of 

 the botanical evolutionist, and it is only well 

 within the present, still youthful century that 

 any light upon it has appeared. 



Darwin, writing in 1879, to Sir Joseph Hooker, 

 said: "The rapid development as far as we can 

 judge of all the higher plants within recent geo- 

 logical times is an abominable mystery," and so 

 it has remained until a year or two ago. Even 

 now the clue that has been found still seems to 

 some uncertain, but it is at least well worth our 

 following. 



