242 PEINOIPLES OP PLANT-TEEATOLOGY. 



grooTes ; one is partly external and partly internal 

 with a dorsal groove on its inner half only (these in 

 all probability represent a fusion between a petal and 

 a sepal, causing thereby the 5-merous condition of the 

 flower) ; two are completely internal, with dorsal 

 grooves on both sides (PI. LII). 



This 2 + 3-merous perianth of Lilium may be 

 compared with the normal structure of certain Resti- 

 aceae and Triuridae, but in this case the condition is 

 due to suppression of an outer leaf, as Celakovsky 

 points out. He also cites a similar normal case to 

 this in the Polygonaceous genus Podopterus. The 

 2 + 3-merous perianth of the knotweed {Polygonum) 

 is therefore probably also due to the same cause. But 

 in all these cases the common factor is the derivation 

 of the 2 + 3-merous perianth from an original 3 + 3- 

 merous one, like that in the dock (Bumex) and the 

 normal flower of Lilium. 



We have therefore in these 5-merous perianths, 

 normal and abnormal, a transition between two 

 whorls (an outer of three and an inner of three), 

 in which the third leaf * is partly, so far as insertion is 

 concerned, in the inner and partly in the outer whorl. 



These terminal 6-merous flowers of Lilium (only 

 flowers in this position showed the feature) are exactly 

 comparable to the 5-merous flowers (in all whorls 

 save the pistil) of the barberry (Berberis) in which 

 genus the lateral flowers have a calyx of 3-merous 

 whorls. Bichler points out that this 5-merous calyx 

 of the terminal flower of Berberis, as also the 5-merous 

 calyx of most Ranunculacese and all other Dicoty- 

 ledons, may be regarded as derived from, or equivalent 

 to, an outer whorl of two and an inner whorl of three 

 members; this is shown by the fact that often the 

 two outer members are laid down a considerable 

 interval before the three and following members 

 appear. This is regularly and normally the case with 

 tke calyx of Oruciferse, and other Rhoeadales, some of 



* Counting from below. 



