558 



NATURE 



[Oct. 13, 1 88 1 



THE EVOLUTION OF THE CRYPTOGAMS'- 



II. 



'X'HE direction and many of the gradations thirough 



J- whicli the highest classes of the vegetable kingdom 

 have been developed from the lower are preserved in the 

 pateontological record. In order to decipher them, how- 

 ever, certain facts must be kept in view : chiefly, that the 

 higher and more complex organisations, are the most 

 susceptible to changes in the external conditions upon 

 which they are dependent, and therefore more readily 

 destroyed, while the simpler the organisation the more 

 yielding or plastic it is, and the greater the chance that it 

 will be able to survive by adapting itself to change. Thus 

 the superb Cryptogams of the Carboniferous succumbed 

 no doubt to great physical changes, but the more humble 

 of them bent to the new conditions, and even found 



therein an impetus leading to unexpected developments, 

 which eventually carried them far beyond their more 

 advanced brethren. 



Tracing back the origin of vegetable life, we see that 

 it consisted nearest its source solely of AlgK. A little 

 later, Cryptogams appeared, and developed their maxi- 

 mum during the Palasozoic period. Next, almost syn- 

 chronously, Gymnosperms are met with, and after a long 

 time preponderate ; and then Angiosperms, obscure and 

 subordmate at first, begin, towards the close of the 

 Secondary period, to take the first rank. 



iVlost of the lowest Algae, such as Ulva and Conferva, 

 are scarcely of a texture to have left traces of their 

 existence, but eight still existing Diatoms have been 

 discovered in British Coal. 



The next group, morphologically, of Algae — the Sipho- 

 nea? — have been shown by M. Munier-Chalmas to be 



Fig, u—BihHtes/i 



abundant in the Trias and Secondary rocks, and to be 

 analogous, or perhaps identical, with the existing Cymo- 

 polia and Acetabularia. It is unfortunate that, owing to 

 the texture of most of the Alga;, observation has to be 

 concentrated on the few groups that could be preserved. 

 In the Silurian the remains of these are numerous, and 

 of forms completely differing from existing types. 



Following the primordial Pateozoic forms, there appear 

 successively the more highly organised Groups, Characeae 

 in the Trias, LaminariaceK in the infra-Lias, and finally 

 Fucaces in the Eocene. 



The Mosses and Liverworts, which seem to indicate the 

 stages through which Algae gradually became adapted to 



" "L'Evolution du Regne Vig^latale." Les Cryptogames. Par MM. 

 baporta et Marion. Bibliutheque Scientifique Internationale, xxxi. (1881.) 

 Continued from p. 75. 



fications ; half natural s 



1 of Bagnols. 



terrestrial conditions, are unknown in the older rocks ; 

 yet, far from assuming that they did not then exist, we 

 should rather consider how exceedingly unfavourable are 

 the conditions under which marine and estuarine strata 

 are deposited to the chance of their becoming imbedded. 



The order Calamareas, as the authors prefer to call the 

 Equisitacea:, include such diverse types as Calamites, 

 Annularia, Asterophyllites, and Equisteum, though 

 Camalodendron and a few other forms are excluded. 

 The group is characterised by the arrangement of their 

 organs in whorls, whether these are true leaves or 

 the modified leaves which support the sporangia. The 

 sporangial whorls either occur together and form a 

 terminal fruit, or are placed alternately with whorls of 

 true leaves, and the sporangial bracts are either disunited 

 or coalesce to form a sheath. Modifications of one or 



