We cannot afford much more space to plant diseases, the farmer has other troubles and we must mention some of them. We cannot leave the subject, however, without a word concerning the mildews. As we have mentioned, they are curious because they dwell outside the plants they attack. Rose mildew is unfortunately all too common in every garden, it may be recognised as a white powder covering leaves and buds. Under the microscope, in the summer we shall find that it consists of a number of thread-like structures, not unlike those of the common white mould and that there are a number of erect chains of spores. Towards autumn, a further examination will show us many round dark-brown structures from which project a number of minute threads. These brown spheres are the winter stage of the fungus, designed to withstand inclement weather. In the spring, the spheres burst and set free a number of minute sacs, each one containing eight spores. The spores germinate on rose leaves and start the disease anew. There will be no difficulty in finding mildews; they are all very similar to the rose mildew in general but they all differ in detail. The gooseberry mildew for example, has a large number of threads running from its winter spheres and each thread is terminated by a little group of branches. The sacs which fall from the opened sphere in the spring, only contain four spores in this case. The animal enemies of the farmer, so far as they concern the microscopist are more difficult to study. Many of them are internal parasites and to gain a real knowledge of their habits and life histories necessitates a good deal of rather unpleasant work for which the ordinary microscopist has neither the time nor the inclination. In order to give our readers some idea of this work, let us take one of the commonest of all agricultural parasites and trace its life history whilst giving hints for its examination under the microscope. The common liver fluke is a worm which, in the adult stage, frequents the liver of some domestic animal, usually the sheep. A friendly butcher will probably be able to supply us with a specimen and, when we receive it, we shall probably dub it a very unwormlike creature. The worms form a large class in the animal kingdom and they do not all resemble the earthworm by any manner of means.