branching mycelium. These threads, sometimes erect, sometimes drooping, flexuous, or prostrate, are composed of numerous roundish or spherical cells attached to each other in a moniliform or bead-like manner (fig. 236). These easily separate from each other. Let a portion of the threads be removed from the leaf on the point of a lancet and laid upon a glass slide, with a thin cover over them. Submit this object to a quarter-inch power, as a drop of water is let fall at the edge of the cover and insinuates itself, by capillary attraction, between the two plates of glass. So soon as it touches the moniliform threads, the disunion commences, and almost before they are enveloped in the fluid, two spherules will scarce remain attached to each other. This delicate little mould on the grass leaf at one time bore the name of _Oidium monilioides_. It is now regarded only as a condition of another minute fungus, to which attention will shortly be directed. The vine disease, so fearfully destructive on the Continent, and not altogether unknown in this country, is another of these incomplete fungi. From an individual who at the time of its first discovery in the south of England took considerable interest in the subject, it was called _Oidium Tuckeri_, which name it continued to bear, both here and abroad, until, with many others, probably nearly all of the same genus, it was found to be only a barren state of what is called by mycologists an _Erysiphe_. The real discoverer of this mildew was undoubtedly the Rev. M. J. Berkeley, who has successfully devoted a long life to the study of these minute organisms, through evil and through good report, and when that study was beset with more difficulties, and received less encouragement than at present. If, towards the autumn, we should again collect some whitened, mouldy, or mildewed grass-leaves, similar in appearance to those mentioned above, and carefully look at them with a pocket lens, little black points, almost as small as a pin-point, or more resembling the full stop with which, this sentence closes, will be found scattered over the white threads. The aid of the microscope must be again sought to make out the structure of the little black dots. Closely nestling upon the mycelium, the little points will prove to be spherical brownish, conceptacles, surrounded with transparent floccose appendages. Many other species are far more beautiful than that of the grass-leaf, as will be seen by reference to our plate. The variation consists chiefly in the form of the appendages which spring from the conceptacle and surround it in a radiating (as in figs. 219, 222, 225, and 230), or in a more or less confused and entangled manner (as in figs. 216, 240, 245, and 251). The surface of the conceptacle is minutely reticulated, and its base is attached to the mycelium. When first formed, these globose conceptacles are almost colourless; they afterwards acquire a yellow colour, and are ultimately of a deep brown.