18 
Blackman and Tansley. 
accordance with the present state of knowledge, and we do not 
think that any entirely satisfactory scheme of the kind exists at 
all. Wille’s treatment of the Chlorophyceae (1890) in Engler and 
Prantl’s PfLanzenfamilien contained the first systematic expression 
of many of the ideas that govern the modern views of the subject, 
hut in many important respects it is now out of date, and the 
second edition of Engler’s Syllabus (1898) does not depart from 
the lines laid down by Wille. The clearest demonstration of the 
inadequacy of the current system comes from the Swedish algologists 
Bohlin 1 (1897 and 1901) and Luther 2 (1899). Some account of their 
work has recently been given by one of us 3 elsewhere, but we are of 
opinion that the results in question are sufficiently well established 
to be incorporated in the classificatory system in general use. 
As it falls to our lot to deliver the advanced courses of lectures 
on this subject at Cambridge and University College, London, 
respectively, we determined to draw up conjointly a scheme Of 
classification of the plants in question so as to obtain uniformity in 
our treatment of the subject, and it occurred to us that such a 
scheme would probably be useful to other teachers. 
Our diagnoses of the various larger groups have been made 
fuller than is usual, with the object of bringing clearly into view 
the relationships of the more important morphological facts, and we 
have added supplementary notes on specially significant points. 
Diagnoses of the leading genera only have been given, and some of 
the less important ones have been omitted altogether. 
The most striking change we have made in Wille’s classification 
is the adoption of the series of Heterokontae 4 established by 
Luther (1899). The forms included in this well-characterised 
series are partly newly discovered and have partly been taken from 
the old groups of Protococcoideae, Siphoneas, and Confervoideae. 
1 Bohlin Studier ofvernagra slagten afalggruppen Confervales 
Borzi. Bihang till K. Svcnska vct.-akad 11 andlingar. lid. 23. 
Afd. 3, 1897. Utkast till de grona algernas ocli arkegoni- 
aternas fylogeni. Upsala, 1901. 
2 Butlier. Ueber Chlorosaccus eine neue Gattung der Siisswass- 
eralgen nebst einigen Bemerkungeu zur Sj'stematik 
verwandter Algen. Bihang till K. Svenska vet.-akad 
Handlingar. Bd. 24. Afd. 3, 1S99. 
3 F. F. Blackman. The Primitive Algae and the Flagellata, 
Annals of Botany, xiv., Dec., 1900. 
4 See Blackman (1900). 
