When the presence of nematodes in plant tissues is known or suspected it is often useful to be able to show the exact situation of the parasites and their biological condition, i.e. whether they are quiescent or active. If plant tissues are teased apart in water active nematodes will be freed and will soon be seen swimming in the water, or, if they are in a state of quiescence, and yet viable, they will revive in an hour or more and become active in the water. Whichever is the case, there may occasionally be some doubt as to whether the nematodes were really in the tissues of the plant or were carried on the outside. The larvae and eggs of most parasitic eelworms are so small that they may easily be overlooked amongst the teased plant tissue, with which there may also be numbers of detached plant hairs closely resembling nematodes in their shape, size and transparency. If the parts of the plants likely to contain eelworms can be stained so that the worms take up the stain in contrast to the plant tissue, and can be seen in their natural position, a much more accurate picture of the situation may often be obtained than that derived from teasing the tissues in water.