Poly gala polygaina and P. pauciflora. 127 



These aerial cleistogamic flowers bring forth fruit with the 

 same rapidity as do the underground ones, and unHke those 

 of the chasmogamic, their fruits generally mature properly. 



It may be here stated in advance that the structural char- 

 acteristics of these green cleistogamic flowers are strikingly 

 intermediate between those of the other two types. Every 

 transition stage from one to the other has been obtained. 

 Series of forms connecting the green and underground cleis- 

 togamics are easy to find. On the other hand, it is not infre- 

 quent to find transition types between the green cleistogamics 

 and those having the fully developed perianth. In this 

 respect our plant calls to mind very strikingly the series 

 of transitions already described for Amphicarpcea by Dr. 

 Schively. 



Comparative Morphology of the Chasmogamic, Aerial 

 Cleistogamic and Subterranean Cleistogamic Flowers. 



We will now pass to a detailed consideration of the mor- 

 phology of the various types of flower. This may best be 

 done by taking up points of structure successively, and com- 

 paring them in the three forms of flower. 



hiflorcscoicc Axis. — In order to describe the rachis we 

 refer for a moment to the structure of the vegetative stem. 

 This has, exteriorly, several winglike angles. The wood 

 appears at an early period as a zone. In an ordinary shoot 

 it is difficult to find traces of separate vascular bundles, since 

 the wood and bast early become continuous rings. The 

 phloem ring is provided with numerous indurated cells. 

 Without is a layer of cortical parenchym six or eight cells 

 thick, limited by a strong cuticle. Incidentally it was noticed 

 that for some reason, when stem sections were treated with 

 iodine, the woody portion presently showed a strong red col- 

 oration. This seemed to suggest the presence of sugar. The 

 reaction took place in various specimens, differently preserved. 



