INTERSPECIFIC INCOMPATIBILITY IN GOSSYPIUM. I. STEM HISTOGENESIS OF G. HIRSUTUM X G. GOSSYPIOIDES

The hybrid of Gossypium hirsutum X G. gossypioides develops normally until 10–12 nodes have been produced at which time neoplasms form in the cortex, phloem, and pith of the lower portion of the shoot axis. Neoplasms are characterized by irregular whorls of unusually large cells the central portions of which contain apparently cytolysed cells and a reddish-brown substance that probably represents the products of cytolysis. Neoplastic invasion is followed by inactivation of the vascular cambium, disorganization of the phloem and cortex, and tylosing and plugging of many xylem vessels. Subsequent growth of the shoot, which continues at a very slow rate for up to several years, involves the proliferation of parenchymatous tissue which becomes secondarily vascularized.