270 THE STORY OF PLANT LIFE 



derived from Dicotyledons. These plants, so far as 

 our knowledge goes at present, appear in time more 

 or less simultaneously with the Dicotyledons. From 

 these reasons, and the difficulty in distinguishing 

 between the possible reduction or the primitive 

 character of certain types of each class, the question 

 as to whether the one is derived from the other, and 

 as to which is the older, if indeed they are not 

 derived from a common primitive or synthetic 

 ancestor, must remain more or less in abeyance. In 

 considering the evidence for and against, however, 

 reference must be made to the works of Miss Sargent, 

 who has done so much work upon the embryology 

 of Angiosperms. Nor must it be forgotten that our 

 knowledge of the early types of these plants preserved 

 in the rocks is at present in a very unsatisfactory 

 condition. This, it is hoped, however, will shortly 

 be remedied by the revision of the Cretaceous plant 

 remains being undertaken by Dr. Marie C. Stopes, 

 who has already succeeded in advancing our con- 

 ceptions of the plant-life of that period so far that 

 the solution of the whole question may be considered, 

 it may be said, as not far distant. 



The leaves in plants of this group are, as in aquatic 

 plants, or geophytes, frequently narrow, with straight 

 or parallel veins, except in Tamus, Paris, as in the 

 Lily group and grasses, etc. Many types, such as 

 the Pondweeds, possess oval leaves, in which the 

 veins are then arc-shaped. In a few types the leaves 

 are round as in Frogbit {cf. Ranunculaceae). The 



