On the blue stem colour in Plagiochila longispina Lindenb. & Gottsche (Plagiochilaceae)

The blue colour of the shoot tips of Plagiochila (sect. Glaucescentes) long ispina is caused by the presence of blue oil bodies in the outer cell layer s of the stem. Oil bodies disintegrate in microscopical preparations after a few minutes and blue-coloured drops accumulate under the cover glass. It is suggested that the substances of these drops become associated with cort ex cell walls during drying of plant material, leading to the blue colour o f these walls in herbarium specimens. (C) 2000 Adac / Editions scientifique s et medicales Elsevier SAS.