DIVISION I. PROTOPHYTA* SACHS, 1874, EMEND. 

 KRASSILNIKOV, 1949. 



(Sachs, Lehrbuch der Botanik, 4 Aufl., 1874, 249; Schizophyta Cohn, Beitr. z. Biol. d. 

 Pflanzen, /, Heft 3, 1875, 202; Krassilnikov, Guide to the Bacteria and Actinomycetes, Izd. 

 Akad. Nauk, U.S.S.R., Moskau, 1949, 41.) 



Pro.to.phy'ta. Gr. combining form protos first (in time), primordial; Gr. noun phylum 

 plant; M.L. pi. noun Protophyta primordial plants. 



Unicellular organisms and organisms which occur in trichomes. Generally these forms 

 are too small to be distinguishable to the naked eye. Ordinarily no differentiation of cells 

 is evident, although those forms that occur in trichomes may show some differentiation 

 into vegetative and specialized cells of various types (heterocysts, holdfast cells and re- 

 productive cells). Increase in number of individual cells is normally effected by simple cell 

 division (fission), rarely by budding; however among the most highly advanced forms, 

 spores of various types may be developed (endospores, conidia or gonidia). In the highly 

 specialized parasites such as the viruses, the processes of reproduction have become so 

 intimately associated with the living protoplasm of the host cells, and the virus particles 

 are so minute (less than 200 millimicrons in diameter) that the e.xact method of reproduction 

 has not yet been determined with certainty. For many years it was believed that these 

 organisms do not possess nuclei; however, in recent years simple types of nuclear bodies 

 have been demonstrated in many of these organisms, and a nucleus, or at least definite 

 nuclear material (chromatin), has been found to be present in all cases. Do not contain 

 chloroplastids, which are found in the cells of the green portions of higher plants. Ubiqui- 

 tous, occurring in the air, everywhere on the surface of the earth, in and on plants and ani- 

 mals and even far below the surface of the earth in mine waters. 



Key to the classes of division Protophyta. 



I. Organisms which possess the photosynthetic pigment phycocyanin in addition to 

 chlorophyll. 



Class I. Schizophyceae, p. 30. 

 II. Organisms which usually do not contain photosynthetic pigments. None contain phyco- 

 c\'anin. 



A. Reproduction by fission. Cells not normally filterable, though filterable stages are 

 known in some species. 



Class II. Schizomycetes, p. 33. 



B. Cells so minute that the exact form of reproduction is not clearly understood as yet. 

 All possess filterable stages. 



Class III. Microtatobiotes, p. 931. 



* The sections which characterize the Division Protophyta, the classes, the orders and in 

 some cases the families have been prepared by Prof. Robert S. Breed, Cornell University, 

 Geneva, New York. 



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