282 



MORPHOLOGY OF THE ANGIOSPERMS 



tion accompanies extreme reduction of the carpels to mere strands of 

 undifferentiated tissue, showing httle resemblance to gynoecia. In other 

 families of the order, tliough Hower structure is much reduced, the 

 gynoecia show evidence of carpel number and limits, and vestiges of 

 ovules are usually present. The Loranthaceae have retained carpellary 



Fig. 110. Diagram showing, in Rubiaceae (where the integument is not reduced), 

 a hypothetical series in reduction. A, PJujllis type, nucelhis cushion-shaped; B, C, 

 Vaillantia types, nucellus flattened, cells reduced in number; D, Riibia ollivicrii 

 type, nucellar cells elongate, filling micropylar canal; B, E, Bouvardia and Oldcn- 

 landia types; E, nucellar cells further reduced in number; F, Houstonia type, nucel- 

 lus and micropylar canal lost. ( After Fagerlind. ) 



structure, without vestiges of ovules; the placental column is reduced 

 to a few cells at the base of the carpels. 



The structure of the ovule of the Rubiaceae, especially that of Coffea 

 and Houstonia, has been much discussed. In this family, though re- 

 duction of the nucellus is strong, the integuments remain well devel- 

 oped. Figure 110 shows theoretical steps in this reduction. The uniseriate 

 nucellus A is reduced in size and cell number in B, and E; its cells be- 



