ALBERT

Description: This book is an exploration into the field of Plant Morphology. It deals with the placentation of the ovules in ten families of Centrospermae \xe2\x80\x94 including the Cactaceae \xe2\x80\x94 and in the Primulaceae. The core is formed by a very close observation and a complete documentation of the histogenesis of the ovary wall, the septs, and the placentae in four Caryophyllaceous species. Furthermore, the result is compared with similar known and newly discovered features in other species and in the other families.\nIt appears that the ovary is composed of a cup of sterile phyllomes which surrounds a central body. This central part is built up by two alternating sets of five axial placentae bearing the ovules. The septs grow from the cup inwards and fuse with the placentae and their ovules. The pattern of the vascular bundles is in full accordance with the histogenetic results. Variations on this theme occur in the other species and families, the ultimate stage in reduction being an ovary with a solitary terminal ovule. However, the Primulaceae do not fit in this scheme; they cannot be considered as Centrospermae.

Description: Descriptions are given of the flowers, fruits, and seeds. The petals have basal scales. The pistil is an urceolate structure issuing in 5\xe2\x80\x947 stigmas. In it are two whorls of ovules along the wall, the lower whorl in the same radial planes as are the stigmas, the upper whorl in alternate radii. The pistil wall is entirely covered by nectariferous hairs. There is a peculiar vascular bundle pattern. The ovule is sessile and atropous, the nucellus is beaked, the inner integument terminates into 2\xe2\x80\x944 projections, the outer integument into 2\xe2\x80\x944 lobes. The ovules develop into inferior seeds mainly by proximal growth. Lobes of the endocarp grow around the ectostome. The testa has its hard layer in the middle. The seeds consist of two parts, a hard container containing a free kernel, an air mantle being enclosed. This is probably a swimming device. As, moreover, the fruit is pulpous, the species probably is diplochorous. The results are put against the theory of metamorphosis and the carpel theory. It is thought that this Malaysian plant is a very unusual, possibly ancient, monotype.

Description: Recently a review on the Angiosperm ovule has been published by the well-known Indian botanist V. Puri (1970). In this review the author stressed the differences between Angiospermous and Gymnospermous ovules, and he refused to accept their comparability or common descent. In this respect Puri comes close to Eames (1961). Both authors tend to regard the ovules as complex emergences. Apart from the main theme, there is a striking passage in this review dealing with the Hugo de Vries Laboratory at Amsterdam. According to Puri in that laboratory facts are sacrificed for hypotheses (p. 10). In the following we would like to start with the facts concerned and present them in a more convincing way, and then ask some simple questions on the structure of the ovules in order to show just how little precise information is available. This lack of information has had the effect of producing many different hypotheses.\nBoesewinkel and Bouman (1967) reinvestigated the initiation of the single integument in some Juglandaceous ovules. In a histogenetic study they showed that the development starts with subdermal and is followed by dermal periclinal divisions. They also stated that the integument arises as two halves, or valves, which are free above but become fused below especially in later stages. Unfortunately, however, they failed to give an unequivocal demonstration of this paired development by means of some good photographs. It was this lack of proof that led Puri to reject the evidence. However, it should be reported that earlier Shuhart (1932) and Leroy (1954) had published the paired initiation of the integument lobes (in Carya spec. and Platycarya strobilacea resp.), and had given photographs of microscopic slides showing cross-sections of the distal part of the nucellus flanked by two opposite tips of the young single integument. In the present paper we present two similar photographs, one of Pterocarya fraxinifolia, the other of Engelhardia spicata. In addition two other \xe2\x80\x98true to nature\xe2\x80\x99 photographs are given, showing two developing ovules of Pterocarya fraxinifolia, as they can be observed directly under a stereo dissecting microscope at low magnification, after the young pistil wall is carefully removed. There is no escape from the fact that the integument in these plants grows like two fusing lobes. The hypotheses are a different matter.

Description: In this treatise \xe2\x80\x98De l\xe2\x80\x99Ovule\xe2\x80\x99 Warming (1878) remarked that although the borders of the integuments grow uniformly, very rarely a division into lobes can be observed. He mentioned Symplocarpus foetida (inner integument four-lobed), Lagarosiphon schweinfurthii (outer integument four- or five-lobed) and Juglans regia (two-lobed). Moreover he cited the report by some authors of an occasional occurrence of lobed integuments in a few more plants.\nMore recently Leroy (1955) described bilobed single integuments in Juglans and Platycarya. Boesewinkel and Bouman (1967) demonstrated that these lobes arise as two separate primordia in Pterocarya and Juglans.

Description: A peculiar structural detail, occurring during the development of ovules, seems to have passed almost unnoticed till the present day. It concerns the distal rim of either the outer or the inner integument, which appears to be slightly lobed in the ovules of several unrelated plants. In a recent note (1970) I called attention to this feature.\nIt is known from Juglans and Platycaria (Warming, 1878; Leroy, 1955; Boesewinkel and Bouman, 1967), where the single integument is two-lobed. Warming mentioned two more cases, namely Lagarosiphon and Symplocarpus; however, I cannot confirm his observations from dried material. I noticed it myself in Scyphostegia horneensis, in Caloncoba welwitschii, and in Sterculia alexandri. In these three species the lobes occur at the rim of the outer integument. To these can now be added Hernandia peltata. However, in that species the lobes occur at the rim of the inner integument.

Description: There are seeds that, when cut in any plane, show a labyrinth structure (van Heel, 1970). This may be due to folding of the cotyledons (Burseraceae, Dipterocarpaceae), or to the presence of testa tissue within the seed. In the latter case the testa tissue may either be located in the endosperm only (\xe2\x80\x98ruminated seeds\xe2\x80\x99 in Palmae, Annonaceae, etc.), or the testa tissue may interfere with the cotyledons. It is possible that in some cases the testa at first interferes with the endosperm, and later on, when the embryo has become larger, also interferes with the cotyledons (Corner, 1966, in some Palmae).\nIn the case of testa tissue interfering with the cotyledons, there are probably two possibilities. Firstly the testa may be located between portions of folded and lobed, mostly flat, cotyledons \xe2\x80\x94 sometimes surrounded by a small amount of endosperm \xe2\x80\x94 (Kingiodendron, Erycibe, Argyreia, Neokeithia). Secondly the testa can be located in many crevices in massive cotyledons (Hernandia, Mangifera). However, it seems that a distinction among labyrinth-seeds will be rather arbitrary, as long as the precise ways of development remain unknown. It is very probable that different ontogenies may yield much resembling end-stages (Corner, 1966; van Heel, 1971; Periasamy 1962).

Description: The seeds are inferior. Only in the apical part of the seed the testa is integumental; for the greater part it is chalazal. A thick mesotesta is formed by a matted layer of sclereids. The chalazal part of the ectotesta is richly vascularized. A sheath of inverted vascular bundles occurs on the inside of the chalazal part of the mesotesta. The seeds are albuminous, the cotyledons foliaceous. An inside cavity may make the seeds float in water. The nucellar beak persists in the ripe seed. The endopyle is five-rayed in c.s., the ectopyle is a longitudinal slit.

Description: The intention of this serial of review papers covering the various branches of botany is firstly to offer the authors a freedom to express opinions and to speculate as widely as they dare upon future trends, and secondly to offer the classical- and modern-minded readers at least a possibility to dip into each other\xe2\x80\x99s pages so that each may appreciate the other and learn \xe2\x80\x98what it is all about\xe2\x80\x99 (Preston, in the preface to Volume I).\nThe present reviewers are engaged in the field of plant morphology and anatomy, to which the last paper of this volume belongs, namely the excellent contribution by P. B. Tomlinson on Monocotyledons (mainly arborescent forms). Tomlinson presents a lively picture of the \xe2\x80\x98habit\xe2\x80\x99, vascularization, inflorescence, etc. in these plants, which were much neglected by one-sided temperate approach during decades. He does so by adding many functional details and by always considering the development of these structures. Especially his scheme for the construction of the stem in the palm Rhapis presents a reliable demonstration based on exact observations.