The Myxamœba grows whilst taking up nourishment from the material in which it lives, and multiplies by division. At a later stage a larger or smaller number of Myxamœbæ may be seen to coalesce and form large masses of protoplasm, _plasmodia_, which in the “Flowers of Tan” may attain the size of the palm of a hand, or even larger, but in most others are smaller. The plasmodia are independent, cream-like masses of protoplasm, often containing grains of carbonate of lime and colouring matter (the latter yellow in the Flowers of Tan). They creep about in the decaying matter in which they live, by means of amœboid movements, internal streamings of the protoplasm continually taking place; finally they creep out to the surface, and very often attach themselves to other objects, such as Mosses, and form sporangia (Fig. 2). These are stalked or sessile and are generally cylindrical (Fig. 3), spherical or pear-shaped (Fig. 4); they rarely attain a larger size than that of a pin’s head, and are red, brown, white, blue, yellow, etc., with a very delicate wall. In some genera may be found a “Capillitium” (Fig. 4 _cp_), or network of branched fine strands between the spores. Flowers of Tan (_Fuligo septica_) has a fruit-body composed of many sporangia (an Æthalium), which has the appearance of flat, irregular, brown cakes, inside the fragile external layer of which a loose powder, the spores, is found. It generally occurs on heaps of tanners’ bark, and appears sometimes in hot-beds in which that material is used, and is destructive by spreading itself over the young plants and choking them. All the motile stages may pass into _resting stages_, the small forms only surrounding themselves with a wall, but the large ones at the same time divide in addition into polyhedral cells. When favourable conditions arise, the walls dissolve and the whole appears again as a naked (free-moving) mass of protoplasm. To the genuine Slime-Fungi belong: _Arcyria_, _Trichia_, _Didymium_, _Physarum_, _Stemonitis_, _Lycogala_, _Fuligo_, _Spumaria_, _Reticularia_. Some genera wanting a sporangium-wall belong to the Slime-Fungi: _Ceratiomyxa_, whose fruit-body consists of polygonal plates, each bearing stalked spores; _Dictyostelium_, in which the swarm-stage is wanting and which has stalked spores. _Plasmodiophora brassicæ_ preys upon the roots of cabbages and other cruciferous plants, causing large swellings. _Pl. alni_ causes coral-shaped outgrowths on the roots of the Alder (_Alnus_). _Phytomyxa leguminosarum_ may be found in small knobs (tubercles) on the roots of leguminous plants. It is still uncertain whether it is this Fungus or Bacteria which is the cause of the formation of these tubercles. _Sub-Division_ II.--=ALGÆ=.