The first forms of life on earth were probably “Protistæ,” which had assimilating colour material, or in other words, they were Algæ because they could assimilate purely inorganic food substances, and there are some among these which belong to the simplest forms of all plants. Fungi and Slime-Fungi must have appeared later, because they are dependent on other plants which assimilate carbon.[2] _Sub-Division I._--=MYXOMYCETES, SLIME-FUNGI.= The Slime-Fungi occupy quite an isolated position in the Vegetable Kingdom, and are perhaps the most nearly related to the group of Rhizopods in the Animal Kingdom. They live in and on organic remains, especially rotten wood or leaves, etc., on the surface of which their sporangia may be found. They are organisms without chlorophyll, and in their vegetative condition are masses of protoplasm without cell-wall (_plasmodia_). They multiply by means of _spores_, which in the true Slime-Fungi[3] are produced in sporangia, but in some others[4] free. The spores are round cells (Fig. 1 _a_) which in all the true Slime-Fungi are surrounded by a cell-wall. The wall bursts on germination, and the contents float out in the water which is necessary for germination. They move about with swimming and hopping motions like swarmspores (_e_, _f_), having a cilia at the front end and provided with a cell-nucleus and a pulsating vacuole. Later on they become a little less active, and creep about more slowly, while they continue to alter their form, shooting out arms in various places and drawing them in again (_g_, _h_, _i_, _k_, _l_, _m_); in this stage they are called _Myxamœbæ_. [Illustration: FIG. 1.--_a-l_ Development of “_Fuligo_” from spore to Myxamœba; _a-m_ are magnified 300 times; _m_ is a Myxamœba of _Lycogala epidendron_; _l´_ three Myxamœbæ of _Physarum album_ about to unite; _o_, a small portion of plasmodium, magnified 90 times.] [Illustration: FIG. 2.--The plasmodium (_a_) of _Stemonitis fusca_, commencing to form into sporangia (_b_); drawn on July 9. The dark-brown sporangia were completely formed by the next morning; _c-e_ shows the development of their external form.] [Illustration: FIG. 3.--Four sporangia of _Stemonitis fusca_, fixed on a branch. _a_ The plasmodium.] [Illustration: FIG. 4.--Sporangium of _Arcyria incarnata_. _B_ closed; _C_ open; _p_ wall of sporangium; _cp_ capilitium.]