Tracheids are the chief water-conducting elements in gymnosperms and seedless vascular plants. They can also be found in angiosperms. Tracheids are elongated cells, closed at both ends. In average are they 1 mm long. They are regarded as the prototype of prosenchymatic cells, since the cell's ends are pointed and real final walls are missing.
Tracheids look often square in cross-section, the lignified secondary wall is relatively thin.
Their entire cell surface is evenly coated. They occur solitarily, statistically scattered, arranged in turns around the middle axis or grouped together. Such groups can often be found at the cell's ends. It is commonly called scalariform. We will meet this structure again, when talking about vessel elements.