Permanent preparations may be secured by the following method: 1. Treat the fresh sections with 1 per cent osmic acid, 5 to 7 minutes. 2. Wash in water 5 to 10 minutes. 3. Treat with a solution of iodine in potassium iodide (0.2 per cent iodine and 1.64 per cent potassium iodide), 20 to 30 minutes. 4. Transfer to 25 per cent sulphuric acid, which should act for at least half an hour; 24 hours may be necessary. 5. Bring the sections into 25 per cent sulphuric acid which has been saturated with iodine. Add a drop of Meyer's pyoktanin solution (1 g. pyoktanin coeruleum in 30 c.c. of water).
In about 5 minutes the sections will be stained sufficiently and can be examined in glycerin. If there are annoying precipitates, remove them with a soft brush.
According to Meyer, the swelling is an advantage only when the walls are very thin. When the walls are thick, the connections show better without any previous swelling.
Try the following method with the seeds of Diospiros, Latania Chamerops, Phoenix) or Phytelephas: Soak in water and cut thin sections. Extract the oily and fatty substances with xylol; wash in 95 per cent, or in absolute alcohol; stain in anilin blue (Hoffman's blue 1 g. dissolved in 150 c.c. of 50 per cent alcohol) for a few minutes. Examine in glycerin. This method succeeds very well with seeds of the date, which is sold at all groceries.
Permanent preparations may be secured by the following method: 1. Fix in 1 per cent osmic acid, or in absolute alcohol, 5 to 10 minutes. 2. Stain for 24 hours in Delafield's haematoxylin. 3. Wash for a few minutes in acid alcohol (5 drops of hydrochloric acid in 50 c.c. of 70 per cent alcohol). 4. Wash for a few minutes in ammonia alcohol (5 drops of ammonia to 50 c.c. of 70 per cent alcohol). 5. Dehydrate in absolute alcohol, clear in xylol, and mount in balsam.
Return to Methods in Plant Histology