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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



has, as it were, insufficient space for a similar crescent-shape base to 

 form a large sheathing base. This appears to be the first indication 

 of the suppression of one cotyledon, as takes place in the Lesser 

 Celandine.^ 



The Return to Land. — Many land plants carry " aquatic charac- 

 ters " in their structure, such as air-chambers, the dislocation of 

 the strands in the stems and petioles, &c. It is therefore presumable 

 that they have had, an aquatic ancestry. A familiar example is the 

 Lesser Celandine {R.anunculus Ficaria). This is now a moisture-loving 

 plant, and often grows to a great size in damp places, as in Malta, 

 where it is called var. calthaefolia, as resembling the Marsh Marigold. 

 It can easily be seen that the stem and petioles contain air-chambers ; 

 the leaves, too, are hairless and heart-shaped, not at all like those 

 of buttercups, but resembling the floating leaves of the Water-lily, 

 Villarsia, and Frog-bit; they also have stomata on the upper sides 

 of the blades : all these are characters found in aquatic plants. 



Now these and other characters, acquired when the Lesser 

 Celandine was fm aquatic plant, are now permanent and hereditary. 

 But such are not always so. They may at first be transient only ; or 

 if the interchange of locality be frequent, as in amphibious plants, and 

 such as grow half in and half out of the water, the aquatic 

 characters may not be at all hereditary, but reappear only when 

 the plant happens to grow in water. If, however, an aquatic 

 plant has lived for many generations in water, then the acquired mor- 

 phological characters become permanent, and appear whenever the 

 plant grows on land. This we have seen to be the case with Ranun- 

 culus heterophyllus and R. trichophyllus . • The anatomical characters 

 are, however, always completely changed in adaptation to air. 



Conclusion. — It will now be seen that the effect upon plants of 

 water is to bring about degeneracy in every organ ; but that, while doing 

 so, this " response " to the *' direct action " of water puts the plant 

 in complete adaptation to it ; so that the most casual observation shows 

 how such plants can multiply to an enormous extent, so as to block up 

 our rivers and canals, sometimes to such a degree as to impede 

 navigation. 



My object in the next lecture will be to show that all Monocotyle- 

 dons, not only aquatic members of this class, but all terrestrial species . 

 as well, exhibit precisely the same characters, proving them to have 

 descended from aquatic Dicotyledons ; though in the case of all the 

 terrestrial species of Monocotyledons now, these have reacquired the 

 microscopical or anatomical structures necessary for an aerial 

 existence. 



* As the single cotyledon of this plant is often notched, it has been thought 

 that this indicates a fusion of the two blades; but such a notch is by no means 

 uncommon where the two cotyledons are present, as in mustard, Convolvulus, 

 &c. There are certain other terrestrial Dicotyledons which have only one 

 cotyledon, and as a coincidence they still have other features which seem to 

 point to a long lost aquatic aiicestry. The European Water Chestnut (Trapn 

 notans), a thoroughly aquatic plant, has only one. It is allied to the Mare's-tail 

 family. 



