NATURE 



72, 



THURSDAY, MAY 26, 1881 



THE EVOLUTION OF THE CRYPTOGAMS 



L' EvobttioJi dit Rcgne Vegetatalc. Les Cryptogames. 

 Par MM. Saporta et Marion. Bibliothfeque Scientifiqne 

 Internationale, xxxi. (1881.) 



THIS exceedingly valuable contribution to the history 

 of the evolution of the vegetable kingdom, to be 

 followed by a second volume dealing with the Phanero- 

 gams, is fully illustrated by 85 figures. 



It is almost superfluous to remark on the exceptional 

 qualifications with which the authors enter upon the task, 

 for they have already produced some of the ablest works, 

 particularly upon fossil plants. Although much of the 

 material they have had to deal with has not been more 

 than usually satisfactory, their work has been singularly 

 free from the arrogance of other writers on the subject of 

 fossil plants, who pretend to a clairvoyance enabling them 

 to determine unhesitatingly even fragments of leaves of 

 extinct trees ^^'^len every organ necessary for botanical 

 determination is absent. When, as in the great majority 

 of cases, subsequent discoveries prove these gentlemen to 

 be wrong, we hear nothing from them, but when their 

 guesses prove right, they are exceedingly jubilant. 



At the outset the authors lay some stress on the fact 

 that a less complex organisation does not necessarily 

 imply relative antiquity. Circumstances exceptionally 

 favourable to certain series of plants have forced their 

 development to a state never afterwards surpassed, but 

 which, on the contrary, has retrogressed by the elimina- 

 tion of hastily-developed or prematurely-adopted types. 

 New series or new branches given off by the same series 

 have constantly replaced, in all ages, the series or the 

 branches which have died out or declined, and the vege- 

 table kingdom, taken as a whole, has constantly pro. 

 gressed. The book, moreover, is not written for those 

 who totally disbelieve in the principles of evolution, for 

 no proof that it contains will convince them ; but those 

 who wish to understand the successive modifications that 

 have led to the comparatively recent group of Angiosperms, 

 will find it full of interest. 



Commencing with the Protista, the authors lead us 

 through the Protophytes to the Lower Metaphytes, which 

 together constitute the artificial group of Cryptogams. 

 These represent an elder branch of the vegetable king- 

 dom, and lead, by perfectly natural transitions, to the 

 Phanerogams, the younger branch, of which the latter off- 

 shoots appeared only at long posterior dates. 



The origin of all plants is in protoplasm, and those of the 

 Protista which are amorphous, yet possess the essential 

 attributes of life, may well be thought to reproduce the 

 probable characteristics of the earliest primordial plants. 

 On the southern shores of France creatures several centi- 

 metres in length are dredged from depths of five to ten 

 fathoms, whose substance is entirely penetrated with fine 

 particles of the sea bottom. They would pass unnoticed 

 did they not shift their position with extreme slowness 

 and extend short prolongations. Placed in a glass of 

 sea-water they attach themselves to the sides, and free 

 themselves gradually of sand, when a slightly yellow 

 hyaline jelly, absolutely deprived of nucleary elements. 

 Vol. xxiv. — No. 604 



is disclosed. They are allied to the Protamceba, Proto- 

 bathybius, and Pelobius, and from these starting points 

 all the progressive stages of development are traced. 



In certain organisms among the Protista the proto- 

 plasmic mass secretes a rigid envelope, and when, further, 

 a portion of the protoplasm becomes converted into 

 another substance, "chlorophyll," all the characters of 

 vegetable life are realised. In the interior of these cells 

 the protoplasm remains truly amcebous, and acts and 

 is acted upon in precisely the same manner as in animal 

 amoeba:, but this special substance chlorophyl gives 

 rise to a whole series of new physiological functions, 

 and its presence alone marks off animal from vegetable 

 life. The only distinction that can be drawn between the 

 two kingdoms is thus entirely due at the commencement 

 to a transformation of part of the elementary protoplasm. 

 Leaving the Protista, the authors treat at some length 

 the embryogeny and methods of reproduction of Proto- 

 phytes, especially the Alga;, tracing these through the 

 primitive and single-celled diatoms and desmids, with 

 soft or hard envelopes containing protoplasm charged 

 with chlorophyl, to the higher forms in which special 

 orsjans are developed, as the Floridea;, Fucacea, &c., and 

 the Characea:. Setting aside the Fungi and Lichens as 

 groups whose development has been arrested by parasitic 

 habit, the authors proceed to consider the manner in 

 which aquatic vegetation became first adapted to terres- 

 trial life. 



While the more highly organised and complex Algae 

 have preserved those aquatic habits necessitated by 

 physiological functions, numerous species of Xostochineae, 

 Palmellea;, and \'aucheria have quitted the water from 

 time to time to vegetate in humid places on land. These 

 furnish the earliest indication of adaptability to aerial life, 

 and it is curious to find that this proceeds from lower 

 forms of AlgK but slightly differentiated from each 

 other morphologically, and not from the more com- 

 pletely evolutionised types. Some, with flat cellular 

 fronds, such as Ulva, crept, it is supposed, face to the 

 groimd and became ancestors of the Hepatica;. Others, 

 more confervoid, produced a thallus whose growth, neces- 

 sarily apical, became complex by simple vegetative multi- 

 plication. Foliary appcndicles were given off, and a sort 

 of plantlet with rootlets, stem, and leaves, all strictly cel- 

 lular, came into existence, capable, like the Mosses at the 

 present day, of agamous reproduction. In the earliest 

 stage of growth of the Equisetacene, of Ferns, and of 

 Ophioglossea:, we see a similar primordial cellular plant, 

 called a Prothallus, develop from the spore, and resem- 

 bling in every respect the lower Algse. This prothallus 

 bears the sexual organs, and it may here be noticed that 

 it is impossible to insist too strongly on the influence exer- 

 cised by the act of reproduction on the differentiation of 

 primordial plants. 



In lowly developed types the act of reproduction arrests 

 what may be termed their nutritive life. This act may be 

 "precocious" or "tardy," the variations in the time of 

 sexuality exerting a dominant influence on the morpho- 

 logic differentiation of life. In the well-known case of 

 the Axolotl the embryos of the same birth may either 

 have well developed or only rudimentary' sexual glands. 

 In the former case the fry reproduce precociously before 

 losing their branchiae, while those which reproduce more 



