338 



EXPEBIMENTS WITH PL A XT S 



shaped leaf, a transition form between the two. Fig. 

 194 shows at (?)) a section of a submerged portion of 

 a ribbon-like leaf, while at {a) is a section of a por- 



194. Cross-section of the ribbon-shaped leaves of Arrowhead, (a) from a part of 

 a leaf above the water, (6) from a part of a leaf below the surface, showing 

 thinness, lack of cuticle and larger air-spaces. 



tion of a ribbon-like leaf which projected into the air. 

 Fig. 195 {a) shows a submerged leaf (water - leaf) of 

 the Water Buttercup, while beside it {!)) is another 

 leaf which grew above the water (air- leaf) . The Water 

 Buttercup presents a transition from a land -plant to a 

 water-plant. If the water sinks, so that the sub- 

 merged leaves are exposed to the air, they dry up and 

 perish, while the air -leaves live on and the plant 

 continues to flourish. 



We have good reason to believe that the water- 

 plants (with the exception of certain groups of flow- 



