2l8 



NATURE 



{yttly 4. 1889 



embryo-sacs of Gymnosperms that occurs in any order of 

 Vascular Cryptogams ; and the same remark apphes to 

 the formation of the microsporanges and pollen-sacs." 

 The structures compared in the latter part of this sen- 

 tence are homologous ; the " secondary embryo-sacs " 

 and megaspores are certainly not so, nor do we see in 

 what sense there is even any "analogy" between them. 



The isosporous series is divided into Lycopodiaceas, 

 Filices, Ophioglossaceae, and Equisetaceee. We are glad 

 to see that some account of Treub's classical observations 

 on the sexual generation of Lycopodium is given. In 

 Psilotum the sporangia are described as " plurilocular," 

 and are then said to be " collected into groups of three or 

 four." These two views of the morphology cannot both 

 be true. 



The class Filices, as here limited, includes the Marat- 

 tiaceae but not the Ophioglossaceae, an arrangement 

 which we do not think an improvement. At p. 71, the 

 steiti of Lygodium is wrongly said to be scandent, in con- 

 tradiction to the correct account given a few pages later 

 on. Slips of this kind are rather frequent in the book, 

 and should be looked to in a future edition. 



The sections on the Ophioglossaceae and Equisetacese 

 call for no special remark, except that we find Sachs's 

 original description of the division of the spore mother- 

 cells in Equisetum reproduced. The process is a perfectly 

 typical case 'of cell-division (not " free cell-formation "), 

 and called for no special description here ; while Sachs's 

 account, however interesting historically, is now fifteen 

 years out of date. 



An interesting notice of fossil Vascular Cryptogams 

 concludes this subdivision. Attention may especially be 

 called to the excellent figure of the stem of Psaronius, 

 which, by the way, is referred to Cyatheaceas^not, as by 

 Solms-Laubach, to Marattiace:e. This chapter will be 

 very welcome to English students. 



The second subdivision, Muscineas, is divided as usual 

 into Musci and Hepaticae. The treatment of these classes, 

 though not very full, is otherwise satisfactory. By an 

 unfortunate mistake, the protonema of the Mosses is twice 

 over described as colourless (pp. 134 and 140). We think 

 that it is undesirable to speak of the archegonia as in any 

 sense " corresponding to the pistil in flowering plants " 

 (p. 141). Expressions of this kind are very likely to mis- 

 lead the beginner, and the same objection applies to the 

 term ''stigmatic cells" for the cells at the apex of the 

 archegonium. 



As mentioned above, the Characeae are separated from 

 the Algae as a distinct subdivision. The reasons given 

 for this separation do not appear sufficient. Much higher 

 morphological differentiation of the vegetative organs is 

 found among undoubted Algit, while the great number of 

 Algal characters presented by the Characeae seem to us 

 to outweigh the points of peculiarity in their reproductive 

 organs. However, the true position of this group is likely 

 long to remain a vexata qucestio. 



The Algae themselves are treated at considerable length 

 (^20 pages), and the account given is the fullest in any 

 general English work. The authors may be congratu- 

 lated on being the first in this country to attempt an 

 adequate summary of our knowledge of these plants : as 

 might be expected, however, there are many points which 

 invite criticism. The Algae are ranged in eight classes: 



Floride^e, Confervoideas heterogamas, Fucaceas, Phaso- 

 sporeae, Conjugatse, Confervoide^e isogamse, Multinu- 

 cleatEC, and Coenobieae. The authors' opinion as to the 

 phylogeny of these classes may perhaps be best repre- 

 sented in a tabular form. All Algae are derived by them 

 from the Protococcoideae, the latter group being placed 

 among the Protophyta. 



Protococcoideae 



Eremobise 



Protococcaceas 



Multinucleatre 



Coenobieae 



ConjiigatcB 



Phaeosporere Confervoideae heterogamre 



Fucaceae 



Florideae 



On the whole, this arrangement seems to us as good 

 as any which has been proposed, though it is necessarily 

 provisional. We cannot agree that the Dictyotaceae con- 

 nect the Fucaceae with the Phaeosporeae through the 

 Cutleriaceae. The resemblance between the latter and 

 Dictyotaceae is a very superficial one. Nor are we satis- 

 fied that Coleochaete really marks the transition from 

 oosporous Confervoideae to Florideae. Falkenberg has 

 already shown how slender the grounds are for this sup- 

 position. We should be disposed to seek the origin of 

 the red seaweeds much lower down in the scale, but in 

 the present state of knowledge it is quite impossible to 

 decide this point. 



The Porphyraceae and Ulvaceae are included among 

 the Florideae as degraded forms. The Ulvaceae, how- 

 ever, have no Floridean characters whatever, and show 

 clear relationships to such Palmelloid forms as Tetra- 

 spora, a fact which the authors themselves recognize (p. 

 418). If, as is possible, Porphyracese and Ulvaceae are 

 really related, the former group will have to be separated 

 again from the Florides, with which it has been some- 

 what too hastily associated on the ground of Berthold's 

 observations. 



It is impossible to consider all the authors' classes in 

 detail. As regards the brown Algae, we do not think it 

 is correct to say that the differentiation of tissues in the 

 Laminariaceae is less strongly developed than in the 

 Fucaceae, and we entirely decline to believe that the 

 unilocular sporangia of Cladostephus are due to the 

 attacks of parasitic Chytridiaceaj ! (p. 250). The Conju- 

 gatae are fully described, but there is some confusion in 

 the use of the words " zygosperm " and " hypnospore " in 

 the order Mesocarpeai. The class Multinucleatae corre- 

 sponds to Siphoneae in the widest sense. We cannot agree 

 with the authors in regarding Vaucheria as the " culminat- 



