Chapters in modern botany / by Patrick Geddes.

  • Patrick Geddes
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: Chapters in modern botany / by Patrick Geddes. Source: Wellcome Collection.

    51/230 page 29
    For Hooker the tendril is a simple prolongation of the leaf such as we see in various leaves, e.g. the lily-climber Gloriosa, while he describes the development of the pitcher as a simple dimpling and deepening of the upper surface near the extreme tip of the tendril, which sui-vives as the mere rudiment already mentioned. He explains this strange development as finding its possible initial rudiment in those water-secreting glands common at the tip of so many leaves, an apparatus which the reader may see at work in the drop which often hangs at the leaf tip of his white Lily of the Nile (lUchardia africand); still better, in many greenhouse arums ; or, best of all, on the dew- gemmed leaves of Lady's Mantle {Alchemilla vulgaris) in a summer morning's walk. Applying our histological experi- ence, too, we may prepare excellent microscopic specimens of these water glands from the leaf tips of Saxifrages or of Indian Cress {Tropceoluni) by carefully scraping away the lower epidermis and parenchyma upon a glass slide in a drop of water, and then turning over the remaining epi- dermis to show its upper surface. Partly from his study of the pitcher leaves of seedling Nepenthes, which appear immediately after the cotyledons, and in which the pitcher seemed to him to develop from the first as a much more important portion of the leaf, Dickson was led to give up this doctrine of Hooker's. The curiously interrupted leaves of some Crotons (C. ititer- rufitus), in which the flat portion, the intervening midrib, and even the pitcher in a rudimentaiy form, are all present, the latter as simply the upper third of the leaf, seemed to him to afford the key to the difficulty ; the detailed develop- ment of the pitcher as a leaf pouching seeming to him essentially similar to that of Cephalotus, above mentioned. Dr. Macfarlane's conclusions as to the nature of the pitchers are very different. He believes that in Nepenthes, Heliam-
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