259 Ferns of Europe and the Atiatific Islands 



data," narrowed gradually from a broad base to the apex ; 

 " decrescens," broadest half or two-thirds of the way down, and 

 the lower pinnce dwindling in size ; and " ambigua," not distinctly 

 either of the other two. Nearly all the compound European ferns 

 are under the two latter, but there are a great many exotic ones in 

 which the decrescent type is shewn very clearly. In the arrange- 

 ment of the veining and divisions, he distinguishes between 

 " anadroma," where the veins and pinnules begin first on the upper 

 side of the midrib or pinnae as the case may be, and " catadroma," 

 where they begin first on the lower side. The three principal 

 types of architecture are the Polystichoid, in which the veins and 

 pinnules are entirely anadromous, the Phegopteroid, in which the 

 pinnules are anadromous in the two lowest pairs of pinnse, but the 

 pinnules catadromous, though the tertiary veins are anadromous 

 upwards, and the Cyatheoid, which only differs from the last in 

 its catadromous tertiary nerves. He distinguishes two kinds of 

 scales, " paleae cystopteroidece," with the cells not incrassated, but 

 lax, elongated, prosenchymatous, and concolorous, and " paleae- 

 clathratae," in which the cells are short and hexagonal, the centre 

 colourless, and the walls thickened and coloured, and keeps up 

 Athyrium as a genus, on the ground that, besides its difference 

 from Asplenium in fructification, its scales are always of the former 

 type, whilst those of Asplenium are of the latter. 



The subject of hybrid ferns is one of the greatest interest. Dr 

 Milde seems quite satisfied that they do really occur, and mentions 

 four cases in which, if we understand him correctly, intermediate 

 forms between well-known species were found in small quantity 

 with the different plants. In three cases out of the four, Asplenium 

 trichomanes was one of the plants, and the others respectively, 

 viride, adiantum-nigrum, and germanicum, and in the fourth 

 instance the two species were Scolopendrium vulgare and Ceterach 

 officinarum. 



In conclusion, we must not omit to say that the book contains 

 a comi)lete monograph of all the known species of Osmunda, 

 Botrychium, and Equisetum, and that upon the latter family Dr 

 Milde is by universal consent the first living authority. He admits 

 in all twenty-five species, and seems to consider that sections of 

 the stems furnish the best characters for their discrimination. 



Those interested in Isoetes will find a full account of the fifteen 

 species which are now known in Europe, two-thirds of which are 

 quite recent discoveries. J. G. Baker. 



