The optimum, minimum and maximum temperatures required for the germination of the spores has been decided in the case of a good many Fungi. A large portion of the most common Fungi have their optimum at 20°C., minimum at 1–2°C, maximum at 40°C. In the case of pathogenic Fungi the optimum is adapted to the temperature of the blood. Fungi living in manure, whose spores are often adapted to germinate in the alimentary canals of warm-blooded animals, have an optimum corresponding to the temperature of these animals, but with a little margin. =Systematic Division.=--The lowest class of the Fungi is that of the PHYCOMYCETES, which have an unicellular mycelium, sexual and asexual reproduction, and have doubtless sprung from sporangia-bearing, lower Green Algæ. From the Phycomycetes (and certainly from the Zygomycetes) spring two well defined branches, each with numerous distinct species; to the one branch belong the HEMIASCI and the ASCOMYCETES, to the other the HEMIBASIDII and the BASIDIOMYCETES. Ascomycetes and Basidiomycetes may be united under the title of MYCOMYCETES or HIGHER FUNGI. The Hemiasci and the Hemibasidii constitute the class of MESOMYCETES. The Hemiasci are an intermediate form between Zygomycetes and Ascomycetes; the Hemibasidii a similar group between the Zygomycetes and Basidiomycetes. Mesomycetes and Mycomycetes have only asexual reproduction; sexual reproduction is wanting. Their mycelium is multicellular. Up to the present time about 39,000 species have been described. Review of the divisions of the Fungi:-- Class I.--=Phycomycetes (Algal-Fungi).= Sub-Class 1. =Zygomycetes.= Sub-Class 2. =Oomycetes.= Family 1. ENTOMOPHTHORALES. Family 2. CHYTRIDIALES. Family 3. MYCOSIPHONALES. Class II. =Mesomycetes.= Sub-Class 1. =Hemiasci.= Sub-Class 2. =Hemibasidii (Brand-Fungi).= Class III.--=Mycomycetes (Higher Fungi).= Sub-Class 1. =Ascomycetes.= Series 1. =Exoasci.= Series 2. =Carpoasci.= Family 1. GYMNOASCALES. } Family 2. PERISPORIALES. } Angiocarpic Exoasci. Family 3. PYRENOMYCETES. } Family 4. HYSTERIALES. } Hemiangiocarpic Exoasci. Family 5. DISCOMYCETES.} Family 6. HELVELLALES. Gymnocarpic (?) Exoasci. Additional: ASCOLICHENES. Lichen-forming Ascomycetes. Sub-Class 2. =Basidiomycetes.= Series 1.--Protobasidiomycetes. Partly gymnocarpic, partly angiocarpic. Series 2. Autobasidiomycetes. Family 1. DACRYOMYCETES. Gymnocarpic. Family 2. HYMENOMYCETES. Partly gymnocarpic, partly hemiangiocarpic. Family 3. PHALLOIDEÆ. Hemiangiocarpic. Family 4. GASTEROMYCETES. Angiocarpic. Additional: BASIDIOLICHENES. Lichen-forming Basidiomycetes.