IRIS VERSICOLOR. BLUE FT.ACx. 



143 



entiation is apparently of no great moment. For this very 

 reason the study of the structure of the flower is all the more 

 interesting, as it serves to show on what seemingly small changes 

 hinge the most wonderful divisions of the vegetable kingdom. 



It is well to keep a Lily flower in view while studying the 

 manner in which the flower of an Iris is built. In the true Lily 

 the perianth is free from the ovary, which latter is therefore 

 called superior in botanical language ; while in the plants of the 

 order Iridacea the perianth is united to the ovary, which is 

 therefore inferior. (See Fig. 3.) As the Iridacece as well as the 

 Lilies are endogens, they have their parts in threes in their 

 normal condition. Thus there are three sepals and three petals 

 in the Lily ; but in the rhythmical development of growth the two 

 verticils have apparently been arrested together, and both sets 

 are therefore so much alike that there seems to be no distinc- 

 tion between them. It is impossible to tell the sepals from the 

 petals, and it would be quite as correct to say that the perianth 

 of the Lily is composed of six petals, as to say that it is com- 

 posed of six sepals. In the Iris the perianth also consists of 

 twice three parts, but it is evident that the verticils have been 

 influenced separately. The three leaves which form the lower 

 verticil, and which may be called sepals, although they are 

 purely petaloid, have broad blades and turn downwards ; while 

 the second verticil has assumed the shape of comparatively 

 small petals which incline upwards. In the stamens we note 

 a still more remarkable difference between the Lily and the Iris 

 than in the perianth. The Lily has six stamens, and these, like 

 the leaves of the flower-cup, are formed of two verticils of three 

 each. It is difficult, however, to distinguish the two series 

 from one another, as they have both been caught, in very 

 close succession, by the same growth-wave ; but if we watch the 

 development of these six stamens, we find that three of the an- 

 thers expel their pollen somewhat before the other three, and from 

 this fact we learn that they really represent two stages of growth. 

 The pistil, in like manner, was originally in a ternary condition, 



