72 PROCEEDINGS OF TUB 



comparable to the ampbigastria of tbe Marcbantias, and, indeed, 

 to the leaves of the JJryophyta generally. 



On the other hand, in the early members of tbe Fern series 

 the Hympodising process went on to a great extent, converting 

 whole groups of thallus-brancbes (cauloids) into appendages, borne 

 on the main supjjorting branches, and tlius leading to the final 

 differentiation of the thai! us into stem and leaf. Small groups of 

 terminal cauloids, forming part of the appendages, became 

 flattened out into pinmdes ; a process which we can see exactly 

 repeated in the modern Flora in plants which convert their 

 branches into cladodes. Thus, according to our author, the Ferns 

 and all the higher groups have true leai'es differentiated out of 

 thallus-branches, while the Lycopods alone retain the simple 

 primitive appendages, which they possess in common with the 

 Bryophytes. Hence all plants above the Thallophytes are divided 

 into Phylloide>is (Bryophytes and Lycopodineaj) and Piiylline.e 

 (Ferns and all remaining classes of vascular plants). In the former, 

 the assimilating organs are still the lamellar phylloids of the sup- 

 posed Prohepatic ancestors ; in the latter they are true leaves, i. e. 

 differentiated parts of the branch-system of the original tballus. 



The Bryophytes are gametophi/fic Phylloideiie, the Lycopodineae 

 sporophiiiic Phylloideje, tbe phylloid appendages being borne in 

 the former on tbe sexual, in the latter on the asexual individual. 

 Thus Mosses and Club-mosses find themselves at last united in 

 one main group I 



Prof. Lignier's idea is interesting. We see how a certain 

 degree of ailinity (though a remote one) may conceivably still be 

 traced between members of the Bryophyte and Pteridopbyte 

 groups, which have been regarded as separated by th,e widest gap 

 in tbe Vegetable Kingdom. But the point which more nearly 

 concerns us is the separation of the Lycopods from tbe rest 

 of the vascular plants. The possibility that tbe leaves of the 

 Lycopods may be essentially different from those of the Ferns, is 

 one which must have occurred to the minds of many botanists. 

 I remember how, nearly thirty years ago, a walk through the 

 Pern-houses at Kew suggested to me and to a botanical friend 

 tie idea that the fronds of Ferns might be really branches, and 

 the leaves of Lycopods scales, comparable to the ran)enta of 

 Ferns. At that time, however, the relation of tbe Ferns to the 

 higher classes of vascular plants was not recognized, so we 

 never extended our idea to the leaves of Phanerogams. 



Fossil Botany tends to emphasize the isolation of the Lycopods, 

 for it shows us no transition between the microphylly of this phylum 

 and the megaphylly of other groups. On tbe contrary, it provides 

 evidence, as Prof. Lignier has shown, that the apparent micro- 

 phylly of certain classes (Equisetales and Conifers for example) is 

 derived from a primitively megaphyllous condition. There is no 

 indication that this applies to the Lycopods ; neither is there any 

 appreciable evidence that their simple leaves ever became modified 



