THE CLASSIFICATION OF PLANTS. XII.* 



JOHN H. SCHAFFNER 

 Department of Botany, Ohio State University 



Eleven papers have been published previously by the 

 writer, giving a preliminary survey of the phyletic classification 

 of plants, and covering the whole ground except the Algae. The 

 first paper was published in the Ohio Naturalist, 5: 298-301, 

 1905, and subsequent papers appeared from time to time in 

 that journal. The present paper completes the series, but it is 

 the intention of the writer to continue the studies in a more 

 detailed manner, dealing with the phylogeny and taxonomy 

 of the various classes and subclasses. 



The term Algae has reference to a physiological group and is 

 of the same convenience in dealing with the lower plants in a 

 practical way as the terms, trees, parasites, herbs, etc. It has 

 no taxonomic value. An alga may be defined as a thallophyte 

 with chlorophyll. The algae are largely aquatic organisms but 

 some species are able to endure aerial conditions as their normal 

 habitat. 



The algae apparently belong to at least six distinct phyla 

 and a number of the classes have closely related fungi. Our 

 knowledge of the morphology and life histories of the algae is 

 still very imperfect, so any arrangement must be regarded as 

 more or less tentative. The writer has not been able to follow 

 those authors who divide the green algae primarily into Akontae, 

 Isokontae, and Heterokont^. Such a procedure seems decidedly 

 artificial. The Peridinieae are regarded as more animal-like 

 than plant-like and are thus removed to the Protozoa. Follow- 

 ing Oltmanns and others, the Diatomeae are placed near the 

 Conjugatae but only as a subphylum, since the relationship 

 can, at best, be only very remote. The agreement with desmids 

 in certain characters is nevertheless striking and both diatoms 

 and desmids may be regarded as derivatives from some prim- 

 itive filamentous group without zoospores, but which discharged 

 its isogamous sexual cells into the water with little change 

 from the vegetative character. Although the Oedogoniaies are 



* Papers f-rom the' Department of Botany, The Ohio State University, No. 127. 



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