THE CARPEL 



199 



pollen-receiving surface involves, for the pollen tubes, a much longer 

 course, but one still largely through the transmitting tissue. 



The transmitting tissue is commonly thought of as filling the stylar 

 canal only, but it was shown as early as the 1870s and 1880s to extend. 



Fig. 77. Transmitting tissue. A, B, C, D, Verbascum thapsus: A, longitudinal section 

 of style and stigma; B, section at o-a in A, c, stylar canal; C, D, cross sections of 

 middle and base of style, respectively. E, F, longitudinal sections of ovaries of 

 Adoxa moschatellina and Fedia conmcopioides, respectively, showing extent of trans- 

 mitting tissue (shaded) in style and ovary; G to K, longitudinal section and cross 

 sections of stigma of Heliotrophim pcnivianum: H, I, ], K, cross sections at levels 

 1, 2, 3, 4, of G, respectively. L, Philodcndwn coidatum, papillose transmitting 

 tissue on receptacle and filaments; M, Vinca minor, papillae with drops of oil at 

 base; N, Heliotrophim pcnivianum, vertical section of border of stigma, shown in 

 G. (A to K, N, after Guegen; L, M, after Capus.) 



in the great majority of families, over the placenta and considerable 

 parts of the ovary wall (Fig. 17 E, F). The presence of a papillose sur- 

 face over areas of the wall where ovules have been lost is probably 

 evidence of primitive laminar placentation. 



The transmitting tissue is formed from superficial carpellary — rarely 

 ovular — tissues, from the epidermis, or from the epidermis and hypo- 



