A Study of the Extrafloral Nectaries of Ricinus Communis

SUMMARY A study has been made of the fine structure and exudate composition of the extrafloral nectaries of Ricinus communis. Actively secreting glands were characterized by the presence of well‐developed swollen endoplasmic reticulum, numerous vesicles, ribosomes and mitochondria, and the occurrence of crystalline (protein) bodies in the nucleus and cytoplasm. Golgi bodies were not prominent. The gland exudate differed from the phloem exudate in a number of respects, particularly in the much lower levels of amino acids and phosphate and the presence of glucose and fructose. Plants with glands removed showed no difference in growth from the untreated controls. The findings are discussed in relation to the possible functions of extrafloral nectaries.