iii8 A TEXTBOOK OF THEORETICAL BOTANY 





B 



Fig. logi. AquUei-ia type of flower vasculation. A, The vascular skeleton of the 



receptacle, spread out. The top series of gaps represent the second whorl of 

 sterile carpel rudiments. B, Upper part of the receptacle showing the course of 



the traces. See text. {AJter Eames.) 



The essential difference between the two types is the fact that in the second 

 type only one kind of perianth part is present and that its vascular supply 



resembles the staminal type rather than the 



TV? lyi fy? sepal type; while in the supply to the carpels 



y - \ / \ / y the ventral traces are not simply branches 



J/\/ \JV \A/ I from the axial system, but consist of the 



entire remainder of that system. 



There are normally no distinct internodes 

 on the floral receptacle, but the axial anatomy 

 frequently shows two intervals in the sequence 

 of organs, firstly between the petals and 

 stamens and secondly between the stamens 

 and carpels. These intervals are not neces- 

 sarily visible externally. 



We have insisted at an earlier point that 

 the variation in detail is just as great in the 

 vascular anatomy of the flower as it is in the 

 morphology of the parts themselves and that 

 it is only in regard to the barest outline that 

 any generalizations are possible. The out- 

 standing conclusions from the receptacular 

 anatomy appear to be that the two categories 

 of perianth parts are distinct in nature, the 

 sepals being normally 3 -trace organs with 

 three trace-gaps in the axial ring, but showing 

 variation between a i -trace, single-gap condition and a multi-trace, multi- 

 gap condition, both of which are exceptional; while the petals, on the other 

 hand, are, with very few exceptions, i -trace structures, agreeing in this 



type 

 the 



Fig. 1094. — Scheuchzeria 

 of flower \asculation. 

 vascular skeleton of the re- 

 ceptacle spread out. Vascu- 

 lar cylinder does not extend 

 beyond the carpel traces. 

 See text. {After Eames.) 



