C0:SF0U^AT10N OF THE GEXUS CTPEIPEDIFJVr. 415 



Tendency to Increase the Inner Row of Stamens. 



It is perLaps worthy of note that in the numerous cases I have 

 examined, wherein the number of stamens in Orchids generally 

 has been increased, the increase has been relatively more frequent 

 m the inner staminal cycle than in the outer; thus, in my 

 experience, it has been more common to find the inner series 

 ai, a 2, and even as, develoj^ed either in a fertile or in a petalodic 

 condition than it has he^n to meet nvith corresponding changes 

 in the outer series Ai, A2, A^. The frequent abortion of the 

 outer row may be indeed induced by the necessities of space, 

 or by the rhythmic alternation of activity and quiescence, which 

 is so marked a feature in plant-life. In the nearly allied groups 

 Burmanniacese and Apostasiacese the inner row of stamens is the 

 one most usually developed, as it is also in Restiaceoe and Xyri- 

 dacese; while in Iridacese, on the contrary, it is the outer episepa- 

 lous row which is usually present, and the inner row is absent*. 



Paetitioj^. 



Under this heading may be included those cases in which an 

 organ, primitively simple, becomes, in course of development, 

 more or less divided by a so-called process of fission. They 

 require to be carefully discriminated from instances of dialysis, 

 or the separation of parts usually concrescent or inseparate. An 

 illustration of this partition was aff'orded by a flower of Cypripe- 

 dium Bpicerianum forwarded by Mr. Hansen. In this flower the 

 dorsal or median sepal, usually entire, had two distinct midribs 

 and a shallow notch at the apex; the lower united sepals, the 

 petals, the lip, the inner row of stamens ai,a2, and the stigma, G, 

 were all of the usual form and appearance.^ The stammode, how- 

 ever, was divided to the base into two polygonal, shield-shaped 

 lobes occupying a lateral, not a median, position. At first sight, 

 therefore, it seemed as if the usual stamlnode representing Ai 

 were absent, while the other two of the outer row A2, As were 

 present in the form of petaloid shields. In fact, the appearance 

 was exactly the same as in certain flowers mentioned in this 

 communication in which the two side stamens of the inner row, 

 ai, a2, were represented by shield-like staminodes. 



* For a case in wliich the inner staminal series in Iris was developed, see 

 Heinricher, Sitzungsb. der k. Akad, Wissensch. Wien, Novembers, 1881, p. 5o9, 

 separate paper, p. 51, tab. v. 



