200 MORPHOLOGY OF THE ANGIOSPERMS 



dermal tissues (Fig. 78). Cell modification, the development of papillae 

 or hairs, and proliferation of tissues form the stigmatic surface. Cell 

 divisions in the epidermis are chiefly tangential; those of inner layers 

 are also largely tangential but may be in all planes. Papillose cells form 

 the most common stigmatic surface. Cells of the transmitting tissue are 

 delicate, more or less elongate, thin-walled cells, sometimes loosely 

 arranged. They are glandular in function, with dense cytoplasm, large 

 nuclei, and often considerable starch. The fluid secreted by them is 

 said to be much like that of pollen-grain cytoplasm. Oil and other 



Fig. 78. Dcgcneria vitiensis. Micropylar part of ovule and adjacent carpellary tissue 

 at pollination, showing transmitting tissue and course of pollen tube to micropyle. 

 (After Swamtj.) 



fatty substances are frequently present, mingled with mucilaginous 

 substances formed by cell-wall breakdown. Chlorophyll is common in 

 all parts of the tissue. Some transmitting cells are simple or compound 

 hairs, as in Zea. Plumose stigmas, such as those of many grasses and 

 other anemophilous taxa, have numerous delicate branches that consist 

 of papillose cells surrounding a single protoxylem element. Pollen 

 grains reaching the stigmatic tissue are retained by entanglement among 

 the projecting cells or are held on cell surfaces by their rough exines or 

 oily surfaces, or by the mucilaginous or sugary secretions of the stigmatic 

 cells. 



Cells of the transmitting tissues, especially those of the stylar canal 

 and of the upper ovary wall, may become separated by the dissolution 



