The structure of the epiphyllous appendages of Begonia hispida var. cucullifera

Abstract

The upper side of the leaves of Begonia hispida Schott. var. cucullifera Irmsch. Bears appendages that may be classified as hair-like and leaf-like appendages. In addition, trichomes occur. Externally, the two classes of epiphyllous appendages and the trichomes are continuous. Anatomically, a discontinuity exists between the trichomes and the most hair-like appendages. The former lack vascular tissue and other tissues such as chlorenchyma, a hypodermis, and typical epidermis. The hair-like appendages, the leaf-like appendages, and the intermediates between them share the following common element of construction: they terminate in an attenuation at whose base a hump is situated. A vascular bundle supplies this hump and ends in two hydathodes. The smallest hair-like appendages consist only of one attenuation-hump element. In the leaf-like appendages the tip as well as each tooth ends in an attenuation-hump element. The same applies to the main leaves, i.e. the teeth of the main leaves are built in a similar fashion. The anatomy of the epiphyllous appendages, especially the leaf-like appendages, is strikingly similar to that of the main leaf. The leaf-like appendages as well as the main leaves have an upper epidermis with a large-celled hypodermis, palisade and spongy tissue, a lower hypodermis, and epidermis with stomata.