66 



good their hold, for in the succeeding- summer none were found 

 away from the pond. It can hardly be competition with other 

 plants that is the determining factor. 



Pilularia, we have already seen, grows on soft mud that is 

 rarely dried up in the course of the year and it often covers square- 

 yards to the total exclusion of all other plants. At first sight it 

 looks like a species of grass, if it were not for the coiled ends of 

 the leaves showing the circinate habit so characteristic of Ferns* 

 and having dark green globular sporocarps on the creeping stems. 

 The upright weakly erect leaves spring from the nodes and are 

 very simple in structure. The stem is sharply divided into nodes 

 and internodes; from the nodes spring both leaves and roots; the 

 internodes are bare. The anatomy of both stem and root has 

 many interesting features. 



The two distinct families of Heterosporous Ferns, of which 

 Azolla and Pilularia are the types, have the feature of great interest 

 in representing an attempt in the course of the evolution of the 

 Ferns to develop a successful line of heterospory. Similar 

 attempts appear in other groups of the Pteridophytes ; ' in the 

 fossil Calamites amongst the Horse-Tails and in certain Lepido= 

 dendra amongst the Lvcopods. Full success, if that may be 

 measured by the setting up of a strong line which finally reached 

 exoression in the flowering plants was only gained by the extinct 

 allies of the Ferns, the Cvcado-filices among which were Lygino- 

 dendron, Bennetites, Williamsonia, etc., described in the present 

 volume on pp. 67-69 in Dr. Scott's lecture on the Fore-runners of 

 the Flowering Plants. 



The Fore=runners of the Flowering Plants. 



By Dr. Dukinfield H. Scott, M.A., LL.D., F.R.S., 



Past President, Linnean Society ; Foreign Secretary, Royal Society. 



(Read before the Geological Section, January 27th, 1915.) 



TN my Presidential Address to the Society on November 26th, 

 1910, I spoke of the " Seed Plants of the Coal," a section of 

 the Palaeozoic Flora. I am glad to hear that my friend, Sir Daniel 

 Morris, is likely to be lecturing soon on the Eocene Plants of the 

 Bournemouth Cliffs, of which he has been making a study for 

 some time. The subject to-day relates to the Flora of an inter- 

 mediate age — the Secondary or Mesozoic Period. Though not of 

 such immediate local interest as the Tertiary Flora, the present 

 subject comes much more within the range of a Hampshire Society 

 than the Palaeozoic forests, for some of the most important and 

 classical specimens of the Secondary fore-runners of the Flower- 

 ing Plants are found in the Isle of Wight and many others in the- 

 neighbouring counties of Dorset and Sussex. 



