On Plate IV. will be seen many examples of the curious vegetables called respectively algæ and fungi, which exhibit some of the lowest forms of vegetable life, and are remarkable for their almost universal presence in all parts of this globe, and also almost all conditions of cold, heat, or climate. Many of them are well known under the popular name of sea-weeds, others are equally familiar under the titles of “mould,” “blight,” or “mildew,” while many of the minuter kinds exhibit such capability of motion, and such apparent symptoms of volition, that they have long been described as microscopic animalcules, and thought to belong to the animal rather than to the vegetable kingdoms. Fig. 1 represents one of the very lowest forms of vegetable life, being known to the man of science as the Palmella, and to the general public as “gory dew.” It may be seen on almost any damp wall, extending in red patches of various sizes, looking just as if some blood had been dashed on the wall, and allowed to dry there. With a tolerably powerful lens this substance can be resolved into the exceedingly minute cells depicted in the figure. Generally, these cells are single, but in many instances they are double, owing to the process of subdivision by which the plant grows, if such a term may be used. Fig. 2 affords an example of another very low form of vegetable, the Palmoglæa, that green slimy substance which is so common on damp stones. When placed under the microscope, this plant is resolvable into a multitude of green cells, each being surrounded with a kind of gelatinous substance. The mode of growth of this plant is very simple. A line appears across one of the cells, and after a while it assumes a kind of hour-glass aspect, as if a string had been tied tightly round its middle. By degrees the cell fairly divides into two parts, and then each part becomes surrounded with its own layer of gelatine, so as to form two separate cells, placed end to end. One of the figures, that on the right hand, represents the various processes of “conjugation,” _i.e._ the union and fusion together of two cells. Each cell throws out a little projection; these meet together, and then uniting, form a sort of isthmus connecting the two main bodies. This rapidly widens, until the two cells become fused into one large body. The whole subject of conjugation is very interesting, and is treated at great length in the _Micrographic Dictionary_ of Messrs. Griffith and Henfrey, a work to which the reader is referred for further information on many of the subjects that, in this small work, can receive but a very hasty treatment.