September 9, 1898.] 



SCIENCE. 



339 



named by Dr. F. H. Knowlton Calcisphwra 

 Lemoni. 



Both of the great families of the Bryophyta, 

 the Hepatica3 and the Musci, are found in the 

 fossil state. Of the former the best known be- 

 long to MarchanUtes and closely resemble the 

 common living liverwort Marchantia. They 

 are found as low as the Oolite (M. erectus Leck- 

 enby), but also in the Wealden and the Tertiary. 

 For the family of mosses Mr. Seward does not 

 even mention the numerous well authenticated 

 forms so common in the peat bogs of Europe 

 and in the amber, but confines himself to the 

 ancestral types that have been called Musciles, 

 one of which (M. polytrichaceus Renault and 

 Zeiller) dates back to the Carboniferous. The 

 absence of this type throughout the entire Meso- 

 zoic is doubtless accidental and will perhaps be 

 supplied by future research. The other forms 

 thus far known are Tertiary. 



As already remarked, the present volume 

 does not complete the great group or subking- 

 dom of Pteridophyta, dealing only with the two 

 classes Equisetales and Sphenophyllales, and 

 leaving the two most important classes, Lyco- 

 podiales and Filicales, for future treatment. 



The Equisetales include the fossil genera 

 Equisetites, Phyllotheea, Schizoneura, Cala- 

 mites and Archxocalamites. These are all very 

 fully discussed, and although the literature is 

 large, especially that relating to the Calamarife, 

 still much of the information contained in this 

 work is either new or supported by fresh illus- 

 trations. The author follows largely the line 

 of Williamson's work, and his conclusions can 

 be relied upon as the last word that the science 

 has to offer. It would be too much to follow 

 the various steps in his reasoning, and it must 

 suffice to point out that, while retaining the 

 genus Archxocalamites of Stur from the De- 

 vonian and Lower Carboniferous (Culm), he re- 

 gards these pithcasts as probably forming a 

 transition from true Calamites to Sphenophyl- 

 lum, or, rather, to use his language, "we have 

 evidence that the Calamites and Spenophyllum 

 were probably descended from a common an- 

 cestral stock, and it may be that in Archxo- 

 calamites some of the Spenophyllum characters 

 have been retained ; but there is no close affinity 

 between the two plants." 



That Mr. Seward should have erected the 

 single fossil genus Sphenophyllum into a class, 

 Sphenophyllales, coordinate with the Lycopo- 

 diales, that include the Lepidophytes and the 

 Filicales, or ferns, may surprise some botanists, 

 but it must be remembered that, notwithstand- 

 ing a certain superficial resemblance, Speno- 

 phyllum has persistently refused to identify 

 itself with Calamites or Asterophyllites, and 

 that from the standpoint of internal structure, 

 so far as known, it has proved wholly unique 

 among fossil plants. 



In 1894 Messrs. "Williamson and Scott, after 

 the most prolonged investigation, declared that 

 " the geuvis Sphenophyllum cannot be placed in 

 any existing family of Vascular Cryptogams. 

 Anatomically there are some striking points of 

 resemblance to Lycopodiacese, but the habit 

 and fructification are totally different from any- 

 thing in that order. Sphenophyllum, in fact, 

 constitutes a group by itself, which is entirely 

 unrepresented in the present epoch, and the 

 affinities of which cannot be detei-mined until 

 additional forms have been discussed."* Mr. 

 Seward scarcely more than iterates this view 

 when he says that " the genus Sphenophyllum is 

 placed in a special class, as representing a type 

 which cannot be legitimately included in any 

 of the existing groups of Vascular Cryptogams. 

 Although this Paleozoic genus possesses points 

 of contact with various living plants, it is gen- 

 erally admitted by paleobotanists that it con- 

 stitutes a somewhat isolated type among the 

 Pteridophytes of the Coal Measures. Our 

 knowledge of the anatomy of both vegetative 

 shoots and strobili is now fairly complete, and 

 the facts that we possess are in favor of exclud- 

 ing the genus from any of the three divisions of 

 the Pteridophyta." He then proceeds with full 

 descriptions and excellent illustrations to work 

 out all the characters of the genus. There 

 is scarcely a better example of what has been 

 called a comprehensive or prophetic type in 

 botany, and Mr. Seward has well expressed 

 this view in the following words : " To put the 

 matter shortly, Sphenophyllum agrees with some 

 Lycopodinous plants in its anatomical features; 

 with the Equisetales it is connected by the ver- 

 ticillate disposition of the leaves, and some of the 



*Proc. Roy. Soc, London, Vol. LV., p. 124. 



