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When she was elected a Fellow of the Royal Society in 1946, Agnes Arber (1879–1960) was one of only three women to have been admitted into the institution. Arber conducted research that focused mainly on the morphology of flowering plants, but her work is characterised by its explorations of historical botany and evolution. First published in 1950, this book widens the scope of morphology into a study of all aspects of form across the whole chronology of botany. Arber begins with Aristotle and investigates the work of early modern botanists like Bacon and Goethe, before examining the effects of this wider approach on subjects like evolution and taxonomy. Arguing that post-Darwinian doctrine often causes botanists to twist their observations to suit a hypothetical history of phylogenesis, rather than changing the hypothesis to suit observational facts, this bold and fascinating text will interest students of biology and philosophy alike.

With thirty-two Figure* in the Text PAGE I. THE ' PHYLLODE THEORY ' FROM THE STANDPOINT OF EXTERNAL MORPHOLOGY. I. De Candolle's 'Phyllode Theory" 466 3. The relation of the ' Phyllode Theory' to the theory of the origin of Monocotyledons through adaptation to the geophilous habit 468 3. The relation of the ' Phyllode Theory' to the theory of the aquatic origin of Monocotyledons ............... 469 4. The 'Lamina' in certain Monocotyledonous leaves ........ 470 6. An extension of the ' Phyllode Theory ' to the leaves of certain Gymnosperms. .. 473 II. THE BEARING OF ANATOMICAL EVIDENCE UPON THE 'PHYLLODE THEORY'. Agues Arber.-Tfie Phyllode Theory of I. THE PHYLLODE THEORY FROM THE STANDPOINT OF EXTERNAL MORPHOLOGY. I. De Candolle's 'Phyllode Theory'. T HERE is now a considerable balance of evidence in favour of the view that the Monocotyledons are descended from Dicotyledonous ancestors. If this theory be accepted, it should become possible to trace homologies between the various organs occurring at the present day in the two groups, since both these groups are thus regarded as the modern representatives of an original common stock. From this point of view, the only structure in the mature plant which presents any difficulty is the leaf. The typical Monocotyledonous leaf is of a simple, more or less linear, form, with a sheathing base and parallel veins: how is such a leaf to be compared with that of a Dicotyledon, consisting, in its fullest expression, of leaf-base and stipules, petiole and net-veined lamina ? J This question has naturally attracted the attention of morphologists, and an interpretation, which has become known as the ' phyllode theory', was put forward, with some reservations, by de Candolle 2 not much less than a century ago. According to this view, the typical Monocotyledonous leaf does not correspond to the complete Dicotyledonous leaf, with its leaf-base and stipules, petiole and lamina, but is merely the equivalent of a petiole with a sheathing base. On this interpretation, the Monocotyledonous leaf, in spite of the reduction which it has suffered, still includes within itself, in many cases, parts derived from each of the two developmental regions of the leaf-the ' Oberblatt', which normally produces the lamina and petiole, and the ' Blattgrund' or ' Unterblatt', which gives rise to the leaf-base and stipules ; 8 or, to use Bower's 4 terminology, it is derived from the hypodium and mesopodium, the epipodium having been lost. It seems to the present writer probable, however, that in some cases reduction may have gone still farther, so that the leaf-base is alone represented, the leaf thus being derived from the hypopodium only. 6 The phyllode theory is supported by the existence of a number of examples among Dicotyledons in which organs not dissimilar to typical 1 In the Phanerogams, with which in this paper we are alone concerned, the differentiation between lamina and petiole has become so 6rmly established that we are justified in treating these two regions as morphological entities. But ...

Summary In the introduction to this study, the chief phases in the interpretation of the flower, from Goethe's day onwards, are briefly indicated in their historical sequence. Goethe's theory of the equivalence of the vegetative shoot to the flower, in the angiosperms, is then discussed and an attempt is made to evaluate the evidence for it. It is shown that this theory, if understood in a broad sense, harmonizes with the modern holistic trend in morphology. It is suggested that the flower is comparable with a vegetative shoot in a condition of permanent infantilism. Special emphasis is laid upon the inflorescence as offering, in some respects, an intermediate term between the vegetative shoot and the flower. After a brief consideration of bracts, sepals, petals and stamens, the Candollean theory of the carpel is discussed, and it is concluded that it has been peculiarly successful in providing a framework for the vast plexus of facts which it is its task to correlate. Some of the difficulties which have been felt in regard to this theory are considered, with special reference to recent work on the gynaeceum structure of the Papaveroideae. The stigma and “transmitting tissue” are then discussed, and it is concluded that there is nothing in the behaviour of this tissue which is out of harmony with the Candollean theory of the carpel. An attempt is made to arrive at a more precise notion of the meaning to be attached to correspondence, equivalence and homology, when these terms are used in connexion with Goethe's comparison of the vegetative and reproductive parts. It is suggested that these terms are best translated into the language of modern thought by the word parallelism, thus avoiding the use of Goethe's type concept, which cannot be safely employed unless its abstractness is constantly borne in mind. The nineteenth‐century phase, in which morphological ideas were lifted bodily into an historical setting, is then discussed, and emphasis is laid upon the danger of thus confusing two irreducible worlds of thought. Certain attempts which have been made to relate the flower of the angiosperm to the reproductive organs of plants of earlier geological periods are briefly criticized. In the concluding sections, attention is drawn to the current reaction against phylogenetic morphology, and in favour of the purely comparative morphology contemplated by Goethe. A slight sketch is given of Delpino and Troll's theories of the flower, in which “form” is considered as distinct from “organization”. Whether these views are accepted or not, the “Gestaltlehre” is at least an indication that the morphological ideas, which Goethe initiated before the end of the eighteenth century, may even to‐day suggest fresh approaches to the problem of the interpretation of the flower.

Jacques d'Alechamps (1513-1588) [Wood-cut, ciica 1600, Department of Prints and Drawings, British Museum]. Enlarged ......••••• 97 51. "Ornithogalum magnum" [d'Alechamps, Historia generalis plantarum, 1586] 99 52. "Tabaco" = A^/t-(?/M«a, Tobacco [Monardes, Joyful! newes out of the newe founde worlde, 1580] 105 53. Text-fig. 22. "Walwurtz m7i.-aYX\VL" = Symphytum, Comfrey [Brunfels, Herbarum vivse eicones, Vol. I. 1530].