2 1 4 TEA LL OPHYTES . 



3f a beautiful blue, in reflected light (by fluorescence) of a blood-red colour. In 

 addition to these two is found also a third yellow colouring material in small 

 quantity, which also, in addition to chlorophyll, causes the colour of Diatoms. 

 Ln Fucaceae, according to Millardet, the chlorophyll, which is undoubtedly present, 

 s concealed by this yellow and by a reddish-brown substance ; the Florideae appear 

 )f a beautiful rose-red, violet, or similar colour, because a red colouring material 

 soluble in cold water is mixed with their chlorophyll in such quantities that the 

 ^reen colour of the chlorophyll is apparent only after this has been extracted, 

 rhese coloured compounds are strikingly constant in large groups of distinct 

 norphological character. 



The Classification of Algae ^ is at present in the utmost confusion; the older divisions of 

 the class into the larger groups and families have, for the most part, been shown, by the 

 recent researches of Thuret, Pringsheim, De Bary, Nageli, and others, to be unsatisfac- 

 tory ; but these researches have not yet been carried sufficiently far to construct a new 

 and complete classification of Algae corresponding to the present requirements of science. 

 The discovery of alternation of generations and polymorphism in some sections justifies 

 the supposition that certain forms not as yet accurately known may be merely conditions 

 of development of unknown cycles of forms, although hitherto considered distinct species 

 and genera. For these reasons I do not, in the following pages, make a systematic 

 review so much as a selection of typical forms round which the remainder group 

 themselves. 



The NosTOCHiNE^ 2, in the broadest sense of the word, form thread-shaped or 

 moniliform rows of cells, usually simple, rarely branched ; the threads are free (in Oscil- 

 latoria), or enclosed in gelatinous sheaths, by the deliquescence of which they are often 

 united into large colonies, which form either roundish or membranous wrinkled masses 

 (e.g. Nostoc). The threads elongate by the longitudinal growth and transverse division 

 of their cells ; only in Seirosiphon and a few allies does any longitudinal division take 



* [The most recent general classification of Cr)'ptogams is that of Cohn (see Hedwigia, 

 eb. 1872, Journal of Botany, 1872, p. 114). The Algee allied to Nostocace^e form the order Schizo- 

 3oreae. In this the family of the Schizomycetes finds a place, including the minute organisms 

 nown in a wide sense as Bacteria. For a detailed account of these organisms see Cohn, Beitrage 

 ir Biologic der Pflanzen, Heft 2, 1872 (Quart. Journ. Micr. Sc. 1873, P- ^S^)- Cohn defines Bac- 

 ;ria as chlorophyll-free cells of spherical, oblong, or cylindrical form, sometimes twisted or bent, 

 hich multiply themselves exclusively by transverse division, and occur either isolated or in cell- 

 imilies. Bacteria make fluids milky unless they have nearly the same refractive index. Their 

 iameter is not more than ^oooo '^^•■> 3-"^ their length varies from twice to 100 times as much. They 

 ivide only longitudinally by elongating to double their normal length and subsequently pinching in ; 

 ley never branch. The cells resulting from the division either separate or remain attached in 

 lains. By the swelling up of their cell-membranes they may form a jelly-like mass or colony 

 ?;oogl8ea). Most Bacteria present a motile and a motionless condition ; their movements in the 

 )rmer are extremely various. The systematic place of these organisms is at present purely provi- 

 onal. E. R. Lankester has shown (Quart. Journ. Micr. Sc. 1873, p. 408), from the investigation 

 F a peach-coloured species which made its appearance in water containing decomposing animal re- 

 tains, that the series of forms distinguished by Cohn cannot be maintained as distinct, and that they 

 lust either be regarded as 'a series of steps in the ontogenesis of a specific form, or they are a number 

 f phases or " form-species " of a Protean organism.' Lister (Quart. Journ. Micr. Sc. 18 73, pp. 393-4) 

 elieves that he has demonstrated the origin of Bacteria from a Fungus, a species of Bematuim. On 

 le other hand, Cohn has remarked the surprising resemblance of the microspores of an interesting 

 >scillarian Alga Crenothrix to Bacteria, although he is disposed to think that there is no genetic 

 Dnnexion between the two. (See Quart. Journ. Micr. Sc. 1873, p. 163.) — Ed.] 



^ De Bary, Flora, 1863, pp. 553 et seq. — Thuret, Observations sur la reproduction de quelques 

 [ostochines : Mem. de la Soc. Imp. des Sci. Nat. de Cherbourg, vol. V. Aug. 1857. 



