STINGING CRYSTALS IN PLANTS.

The results go to show that in the case of plants with stinging crystals, the action consists of two distinct stages: (1) The mechanical action of the raphides in piercing the skin; (2) The entrance through the minute wounds of a proteolytic enzyme which is the cause of the greater part of the effect The removal of the crystals by filtration or the destruction of the enzyme will not eliminate all the irritating properties, but the two actions together are sufficient, and so the action must be regarded as being produced by combination of the two factors.