- Male Flowerof the Nettle (Urtica).
They may, for instance, be glandular or stinging, as in the common stinging nettle, where the top of the hair is very brittle, easily breaking off when touched.
To these three characters the Hydrozoa add a fourth which is distinctive of the subdivision of the Coelenterata termed the Cnidaria; that is to say, they always possess peculiar stinging organs known as nettle-cells, or nematocysts (Cnidae), each produced in a cell forming an integral part of the animal's tissues.
By means of the stinging nettle-cells or nematocysts with which the tentacles are thickly covered, living organisms of various kinds are firmly held and at the same time paralysed or killed, and by means of longitudinal muscular fibrils formed from the cells of the ectoderm the tentacles are contracted and convey the food to the mouth.
Contracted form (Verticillaster), Dead-nettle, Pelargonium.
The vines whose fruit is intended for table use as grapes or raisins are trained on espaliers or on trees, especially the nettle-tree (Celtis ausiralis)
In Labiate plants, as the dead-nettle (Lamium), the flowers are produced in the axil of each of the foliage leaves of the plant, and they appear as if arranged in a simple whorl of flowers.
- Flowering stalk of the White Dead-nettle (Lamium album).
- Tetramerous monochlamydeous male flower of the Nettle (Urtica).
- Irregular gamopetalous labiate corolla of the Dead-nettle (Lamium album).
T ? ??, teombe Nettle F +e yPa-N+1l.N *'+R Slueumber'??r aC I°nh s 1 E gy jj l '° ° o e^M dc pford?
So also in Labiatae, such as dead-nettle (Lamium), the different whorls of inflorescence are developed centripetally, while the florets of the verticillaster are centrifugal.