May 27, 1875] 



NATURE 



65 



carpels, many tendrils and prickles, &c., are altogether 

 similar (in mode of development) to the green organs 

 which have been termed simply leaves." So with all the 

 other members ; they may be modified to perform the 

 most varied functions. 



The second book, treating of Special Morphology and 

 outlines of Classification, will probably be found to be 

 the most generally interesting part of the work. It 

 gives a clear and valuable account of all the " classes" of 

 the vegetable kingdom, which, according to our author, 

 are thirteen in number, and are to be further arranged in 

 five groups, viz., Thallophytes, Charace^e, Muscineae, 

 Vascular Cryptogams, and Phanerogams. Here the 

 in'dustry and care of the author are well shown, as he has 

 collected from all trustworthy sources, descriptions of the 

 structure and life-history of typical forms of plants. This 

 classification is slightly modified in the appendix, which 

 is taken from the fourth edition. The distinction 

 between the Algas and Fungi, namely, that the Algai 

 contain chlorophyll, while the Fungi do not, is disregarded, 

 and the Alga>, Fungi, and Characea: made into four 

 classes, the characters being taken from the modes of 

 sexual reproduction. It seems a pity that the division of 

 the Vascular Cryptogams into classes was not recon- 

 sidered, as the discovery of the prothallium of Lycopodium 

 breaks down the division into isoporous and hetero- 

 sporous groups. We prefer a division of the vascular 

 cryptogams into three classes : Filicina?, Equisetaceas, 

 and Lycopodinas. The Filicinse include four orders — 

 Filices, Marattiaceae, Ophioglossaceae, and Rhizocarpea; — 

 while the Lycopodina; include three, viz., Lycopodias, 

 Selaginella;, and Isoetea?. The chapter on the groups of 

 flowerless plants are of great interest, and will be studied 

 with pleasure by those who have only seen the meagre 

 s.nd often untrustworthy account given in some of our 

 text-books. 



Passing to the Phanerogams, Sachs considers the dis- 

 tinguishing characteristic of the group to be the formation 

 of the seed. He contrasts the Cryptogams and Phane- 

 rogams, and points out the homologies of the reproduc- 

 tive organs. " This organ (the seed) is developed from 

 the ovule, which, in its essential part, the nucleus, pro- 

 duces the embryo-sac, and in this the endosperm and 

 the embryonic vesicle. The latter is fertilised by the 

 pollen-tube, an outgrowth of the pollen-grain, and, 

 after first growing into a pro-embryo, produces the 

 embryo. The phanerogamic plant, which is differ- 

 entiated into stem-leaves, roots, and hairs, corre- 

 sponds to the spore-forming (asexual) generation of vas- 

 cular cryptogams ; the embryo-sac to the Macrospore ; the 

 pollen-grain to the Microspore : the endosperm is equi- 

 valent to the female prothallium j and the seed unites in 

 itself, at least for a time, the two generations, the Pro- 

 thallium (endosperm) together with the young plants of 

 the second (sexual) generation (the embryo)." Throughout 

 the whole of the chapters of the second book, the influence 

 of the " Theory of Descent" is very evident. Sachs, how- 

 ever, withdraws, in the fourth edition, the pedigree of the 

 vegetable kingdom, which he sketches in Book III. of the 

 present edition. The Phanerogams are divided into 

 three classes, Gymnosperms, Monocotyledons, and Dicoty- 

 ledons. Our author adheres mainly to the Gymnospermous 

 theory, and certainly the question whether conifers are 



gymnospermous or not" has yet to be decided, notwith- 

 standing the recent controversy of Eichler and Stras- 

 burger. 



More than one hundred pages are devoted to the 

 Angiosperms, Monocotyledons, and Dicotyledons. In the 

 remarks on the flowers of Angiosperms, many of our long- 

 cherished ideas, the arrangement of stamens, for example, 

 are rudely disturbed. Monadelphous stamens, as in 

 Malvacccs, are shown to be the result of cohesion of 

 primordial stamens, and subsequent branching. The 

 Polyadelphous stamens of Hypericum are formed by 

 branching of three or five primordial stamens. The use 

 of the English terms "regular" and "symmetrical" as 

 applied to flowers, has been a cause of trouble to the 

 translators, and we cannot but express the hope that both 

 these terms may be quietly dropped into oblivion. On the 

 subject of placentation, the statements of Sachs differ from 

 those usually taught in this country. He shows the 

 relation between the parietal and axile forms, and, 

 making two divisions — viz., the ovules produced by carpels, 

 and the ovules produced on the axis — further subdivides 

 both of these into two : — 



1. Marginal. Ovules for reflexed margins of carpels. 



2. Superficial. Ovules for whole inner surface of the 

 carpel, except on midrib. 



3. Lateral. Ovules produced singly or in numbers 

 from floral axis. 



4. Terminal. Apex of axis bearing nucleus of ovule. 

 The formation of the embryo is very carefully described 



from Hanstein's researches, and the three layers of tissue 

 in the embryo, Dermatogen, Periblem, and Plerom, care- 

 fully figured. The great significance of these layers has 

 probably not yet been fully appreciated, and if it holds that 

 axial structures arise from plerom and lateral appendages 

 from periblem tissues, then a most important guide will be 

 obtained enabling us to determine accurately the mor- 

 phological value of many disputed structures. 



In the classification of inflorescences we have Schim- 

 per's term Dichasium substituted for the incorrect "dicho- 

 tomous cyme" used in English works. This is a marked 

 improvement, as it was always a difficulty to the student 

 to find that, although called dichotomous, it was not so. 

 There is also a great difficulty with the terms heUcoid 

 and scorpioid. Sachs uses Schimper's terms bostryx 

 and cicinnus. De Candolle, in 1827, used the term 

 scorpioid to distinguish the characteristic inflorescence 

 of Myosotis, the scorpion grass. The recent researches 

 of Kaufmann, Warming, and Kraus, show that the in- 

 florescences of Borragineas are sympodial arrangements of 

 dichotomies ; and we do not think there would be any 

 difficulty in retaining the term scorpioid for them. Bo- 

 stryx and cicinnus were used by Schimper in 1835, while 

 it was not till 1837 that the brothers Bravais amended 

 De Candolle's definition of scorpioid and introduced the 

 term helicoid. Schimper's terms, therefore, have the 

 priority, and ought to be used. (See Hofmeister's 

 " Handbuch der Phys. Botanik," vol. i. p. 434). 



The floral diagrams given by Sachs will be found very 

 useful, and we also think that the adoption of the florjU 

 formulas will be a great assistance to the student. Sachs 

 uses the collective terms for the whorls throughout in his 

 floral formulae — calyx, corolla, androecium, and gynoecium, 

 while the translators have substituted the name of the 



