212 A LESSON ON BUTTERCUPS. 



Leaves. Note the length of the stalk at different levels 

 and interpret this with general reference to the normal 

 situation of the plant ; so also the alternate arrangement, 

 general dissected character of lower leaves, sessile and 

 linear type of upper leaves. All these may be regarded as 

 adaptations to a situation in which room is scarce and 

 many shadows are cast. Microscopical examination shows 

 that the stomata (openings for transpiration of moisture) 

 occur mostly on the under side. This is a quite general 

 arrangement which tends to check too rapid evaporation of 

 moisture. The hairs on the surfaces of the plant may 

 also be interpreted in this case as having the same signifi- 

 cance. 



Flowers. The presence of nectaries in this flower sug- 

 gests that it may be visited by insects, and an examination 

 of the flower out of doors will show that this is so. These 

 nectaries are exposed and easily got at, hence they are 

 visited by various types of insect. Flies are common 

 visitors. The pollen is also abundant, and the flowers are 

 visited for the sake of it also, e.g. by small beetles. 



THE WATEE CEOWFOOT OE BUTTEECUP. 



(Ranunculus aquatilis.} 



In contrast to the meadow buttercup, taken as an aver- 

 age illustration of a terrestrial flowering plant, we now 

 examine another member of the same genus, in this case 

 of aquatic habit. Here we need refer only to the special 

 features which may reasonably be interpreted as adapta- 

 tions to the habitat in question. And first let us note that 

 even within the species we shall find specialised features 

 according to whether the plant grows in a rapidly running 

 stream or in sluggish or stagnant water. 



Let us contrast the conditions. We have just described 

 the terrestrial type, noting its needs as regards support in 

 soil, strength above ground for parts bearing flowers and 

 leaves, etc. Now let us look at the water buttercup. 



