Feb. 7, 1884] 



NA TURE 



341 



Ur. Agardh points out that the organs with powers of 

 motion, observed by Derbcs and SoUer, are scarcely to 

 be referred to the Florideffi, because in their eruption 

 from the plant, as well as in their movements, they have 

 an appreciable analogy with the organs of Prasiola, 

 described by the author in a new species, P. cornucopia 

 (see Table III., fig. 74, '-'J,g)- 



On the other hand. Dr. Agardh shows that the chief 

 consideration which induced some algologists to remove 

 Bangia and Porphyra from the Ulvacere to the Florides 

 was derived from the quaternate division of the cells, 

 which was thought to be analogous to the quaternate divi- 

 sion of the tetraspores in the Floridese. He points out 

 that Janczewski and Thuret had observed that it was not 

 tetraspores. but octospores, which resulted from the divi- 

 sion in Porphyra ; and he calls attention to the fact that 

 the so-called octospores are themselves repeatedly divided 

 into new generat'ons of tetraspores and octospores, in 

 the same manner as the cells or cell-contents in Prasiola, 

 Tetraspora, Palmella, Monostroma, Ulva aureola {Ilea 

 fiilvescens), and some species of Enteromorpha divide ; 

 thus showing an analogy with these plants rather than 

 with the Florideffi. 



The author observes that if the organs of Porphyra be 

 considered analogous with the tetraspores of the 1- lorideae, 

 these organs, according to some authors, should possess 

 different functions, the tetraspores being deemed neutral in 

 the Florideae, but the octospores se.xual in Porphyra. If, 

 he says, those organs which in Porphyra are called anthe- 

 ridia agree with the antheri Jia ot the Floridea? ; if, also, 

 those 4-partite organs which constitute spores are to be 

 compared with the tetraspores of the Floridea; ; there 

 still remain in Porphyra and Bangia no organs which can 

 be considered identical with the capsular fruit of the 

 Floridea;. If, therefore, those organs which form the 

 principal characteristic of the Florideae are absent, it is 

 evident that Bangia and Porphyra are far inferior to the 

 Fioridea;, and that very distant affinities must be sought 

 for them. Moreover, if those organs which are neutral in 

 the Floridere become sexual and female in Porphyra, this 

 rather seems to indicate divergence than affinity. 



With regard to J'angia, Dr. Agardh observes that the 

 filaments of this plant growing together in patches, as 

 already observed by DiUwjn and others, always vary in 

 thickness and in appearance, and that this difference of 

 appearance may have suggested the idea that they were 

 of various kinds (male and female filaments). According 

 to Dr. Agardh, these difl'erences are merely differences of 

 age ; and the so-called special organs are to be considered 

 rather as different states during the evolution of the 

 fructification, than as distinct organs. 



Reviewing the statements of different algologists with 

 regard to the fructification of these plants, the author 

 shows from their published works that much difference of 

 opinion existed among them. Thus, according to Derbcs 

 and Solier, those organs in Bangia which they con- 

 sidered as male are said by them to be endowed with 

 lively motion ; while Thuret and Reinke, referring to the 

 same organs, say that they are motionless. Again, the 

 author observes that Janczewski, alluding to the octo- 

 spores of Porphyra, says that they have an amceboid 

 motion ; Thuret, on the contrary, states that they are 

 motionless. 



After quoting Thuret's description (" Etud. Phyc") of 

 the processes of fructification in Porphyra, Dr. Agardh 

 cites the following passage referring to the antheridia : 

 " La division s'arrete plus tot pour les spores et se pro- 

 longe davantage pour les antheridies ; mais il n'y a pas 

 de difference fondamentale dans le procedd On en a la 

 preuve dans les cas anormaux, deja mentionni^s par M. 

 Janczewski, ou le contenu d'une meme cellule primitive se 

 change, partie en spores, partie en corpuscules males.' ' So 

 remarkable does this statement appear to Dr. Agardh 

 that he quotes it also in the note to p. 26, where he thus 



comments on it : " Quomodo ii, qui hoc observarunt, 

 sibimetipsis persuaserint eam partem contentus, qua; 

 organis perhibitis foemineis constaret, sub stadio evolu- 

 tionis panlo posteriore in organa mascula non transmu- 

 taretur, mihi non liquet." 



Leaving this subject to the consideration of algologists, 

 the more general features of the work may now be noticed. 



Dr. Agardh arranges the UlvaceK under the following 

 genera: i, Goniotrichum ; 2, Erythrotrichia ; 3, Bangia ; 

 4, Porphyra ; 5, Prasiola ; 6 ? Mastodia ; 7, Monostroma ; 

 8, Ilea: 9, Enteromorpha; 10, Ulva; and II, Letter- 

 stedtia. 



Of these genera Mastodia and Letterstedtia are natives 

 of the Southern Ocean. Ilea, of which one species only 

 is known, 1. fiilvescens {Ulva aureola, C. Ag.), is a small 

 tubular plant which grows at the mouths of some Swedish 

 rivers. The cells of which it is composed are arranged in 

 series of fours, as in Prasiola, but the colour is dusky as 

 in Dictyota. 



The other genera, of which many species are natives ot 

 these shores, will have more interest for British algo- 

 logists. Prasiola marina, Crouan, which Dr. Agardh 

 unites with P. stipilala, has been recently found in Scot- 

 land and in Devonshire ; and the Ulva calophylla of 

 Greville, and Ulva crispa, have been removed to Prasiola. 



Of the twenty species of Monostroma, five, namely, M. 

 hullosuin, .;/. laceratum, M. quaternarium, M. latissiiniim, 

 and M. witlrockii have been found on our coasts. To 

 these Dr. Agardh adds another species, M. lactuca 

 (U. lactuca, C. Ag.), which he considers identical with 

 M. undulatum of Thuret, and probably with M. pulchriim, 

 Farlow, of the east coast of North America. While thus 

 transferring the specific name lactuca to a Monostroma, 

 the author excludes it from Ulva, where it has been a 

 sourse of confusion. 



With regard to Porphyra, Dr. Agardh agrees with Dr. 

 Greville in considering P. linearis as a distinct species ; 

 and he mentions P. ainethystea as a native of England. 

 Harvey had stated that the latter had been found on the 

 west coast of Ireland, but the plant appears to have been 

 unknown to him, and has not been found until recently, 

 when Mr. G. W. Traill met with it on the east coast of 

 Scotland. Tiie arrangement of the cells in the plant is 

 very beautiful. 



In accordance with the views of most algologists, P. 

 7/ulgaris and P. laciiiiata are united bj- the author ; but 

 he has changed the name of the plant to P. umbilicalis 

 (" L. Sp.," ed. 2, 1633), of which he describes several 

 forms. In his views of the structure of this alga, L>r. 

 .Agardh is at issue with Janczewski and Thuret. The 

 last-mentioned authors state that the vegetative structure 

 of the plant is always monostromatic, and that it is in the 

 fruitful parts only that the cells are arranged in two series. 

 Dr. Agardh, on the contrary, says that the alga is at all 

 times distromatic. A reference to Plate II., fig. 61, /, will 

 show that the two strata seen in the transverse section do 

 not exhibit that subdivision of the cells which consti- 

 tutes the fruit. 



Dr. Agardh agrees with M. le Jolis in removing the 

 Ulva linza of Harvey to Enteromorpha, where it takes 

 the name of E. liii::a. Of Ulva, seven spicies only are 

 enumerated. Under U. rigida there are no fewer than 

 twenty-four synonyms. While, hoA-ever, the author de- 

 serves thanks for clearing away so many reputed species, 

 he describes many forms of this very generally distributed 

 alga. 



Enough has now been said to show the interest this 

 work should have for algologists. It is illustrated by 

 four plates, beautifully executed, containing 124 figures. 

 -Although the title is Swedish, the work is written in Latin. 



Of Rabenhorst's " Kryptogamen-Flora," Nos. 4, 5, and 

 6 of Part II., in which the marine algifi are described 

 by M. Hauck, have recently appeared. Numbers 4 



