280 



MORPHOLOGY OF THE ANGIOSPERMS 



entation is a reduced free central type. In Arceuthohium, the central 

 column and its remnant ovules are reduced to a basal, more or less 

 spherical, central body of undifferentiated tissue — termed by some 

 authors the nipple — in which is embedded the archesporium of two or 

 more ovules (Fig. 108E, F). In some of the Loranthaceae, the projec- 

 tion at the base of the locule is absent; Viscum and Loranthus show no 



Fig. 108. Reduced ovules and placentae. A to D, portions of pistillate flowers of 

 Visciim articulatum: A, median, longitudinal section of young bud; B, part of A, 

 at level of carpel tips; C, D, transverse and longitudinal sections of young carpels 

 at level of embryo-sac mother cells, "placental area." E, F, median longitudinal 

 sections of pistillate flowers of Arceuthohium av^ericanum and A. pusilhim, respec- 

 tively, showing reduced, cone-shaped placenta, nipple containing embryo sacs. G, 

 transverse section of part of placental lobe showing longitudinal section of ovule 

 with integument, Prosopanche hurmeisteri. e, embryo sac; n, nipple; p, perianth; s, 

 stigma; st, style. (A to D, after Treiib; E, after Dowdmg; F, after Thodatj and 

 Jolinson; G, after Van Tieghem.) 



remnant of a central column ( Fig. 108A to D ) . In the cleft ( Fig. 108B ) 

 between the appressed bases of the reduced, connate carpels, a group 

 of hypodermal cells, set apart by their richer cytoplasm, become the 

 archesporium (Fig. 108C, D). 



The Balanophoraceae present the extreme reduction of the ovule, as 

 a part of the remarkable reduction of the entire gynoecium, a reduction 

 to a small, slender structure with weak differentiation of ovary, style, 



