| phyllotaxy | <plant biology> The arrangement of the leaves on the stem. The three common positions are alternate, opposite, and verticillate. When spiral, often expressed quantitatively as the fraction of the circumference of the stem that separates two successive leaves. (09 Oct 1997) |
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| phyllous | <botany> Homologous with a leaf; as, the sepals, petals, stamens, and pistils are phyllous organs. Source: Websters Dictionary (01 Mar 1998) |
| phylloxanthin | <botany> A yellow colouring matter extracted from chlorophyll. Origin: Phyllo- + Gr. Yellow. Source: Websters Dictionary (01 Mar 1998) |
| phylloxera | 1. <zoology> A small hemipterous insect (Phylloxera vastatrix) allied to the aphids. It attacks the roots and leaves of the grapevine, doing great damage, especially in Europe. It exists in several forms, some of which are winged, other wingless. One form produces galls on the leaves and twigs, another affects the roots, causing galls or swellings, and often killing the vine. 2. The diseased condition of a vine caused by the insect just described. Origin: NL, fr. Gr. Leaf + dry. Source: Websters Dictionary (01 Mar 1998) |