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P. Baas

Bio: P. Baas is an academic researcher. The author has contributed to research in topics: Siphonodon & Peritassa. The author has an hindex of 1, co-authored 1 publications receiving 58 citations.

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Journal ArticleDOI
01 Dec 1978
TL;DR: The laterocytic stomata are here recognized for the first time as a distinct stomatal type characterized by the lateral position of the subsidiary cells but yet different from the paracytic and cyclocytic type.
Abstract: SUMMARY The leaf epidermal characters of 89 species belonging to 42 genera of the Celastraceae sensu lato (including Hippocrateaceae) are described in detail. The range and pattern of variation in stomatal type and presence and type of crystalliferous epidermal cells can be used to support the broad family concept of Celastraceae. The stomata may be anisocytic, complex anisocytic, anomocytic, cyclocytic, bi- and/or tricyclic, complex cyclocytic, laterocytic, complex laterocytic, paracytic, parallelocytic, helicocytic, or of an intermediate type. The laterocytic stomata are most common, and are here recognized for the first time as a distinct stomatal type characterized by the lateral position of the subsidiary cells (3 or more) but yet different from the paracytic and cyclocytic type. The general implications of the epidermal diversity for the grouping of genera in a natural classification are discussed. Special attention is devoted to the taxonomic position and/or delimitation of the following genera: Kokoona and Lophopetalum; Sarawakodendron; Perrottetia; Salada and the related genera Cheiloclinium, Peritassa and Tontelea; Hippocratea and the putatively related genera Antodon, Apodostigma, Cuervea, Elachyptera, Helictonema, Hemiangium, Hylenea, Loeseneriella, Prionostemma, Pristimera, Reissantia and Simirestis; Cassine sensu lato (including Elaeodendron, Crocoxylon and Mystroxylon); Denhamia and Maytenus; Euonymus; Goupia; Siphonodon and Pottingeria. Finally a tentative discussion of the wider affinities of Celastraceae is given and the scope for future studies is indicated.

59 citations


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TL;DR: The distribution of mucilage cells in vegetative parts of the dicotyledons is reviewed on the basis of an extensive literature study and their systematic and diagnostic value at different levels of the taxonomic hierarchy is discussed.
Abstract: The distribution of mucilage cells in vegetative parts of the dicotyledons is reviewed on the basis of an extensive literature study. Mucilage or slime cells occur in 144 families, belonging to 47 orders as defined in Takhtajan's system of classification. Their systematic and diagnostic value at different levels of the taxonomic hierarchy is discussed. Although mucilage cells are generally diagnostic at the species level, variation within genera and families seriously limits the systematic significance in mostphylads. The core families of the Malvales, which are all mucilaginous, constitute an exception at the ordinal level, while in a number of genera, families, and orders the distribution of mucilage cells tends to be associated with natural groups. In most families and orders of the subclass Asteridae, mucilage cells are absent from the vegetative organs. Development, ultrastructure, histochemistry, and distribution of mucilage cells are briefly reviewed. In almost all well documented cases, m...

139 citations

Journal ArticleDOI
TL;DR: A recent review of the classification and geography of the Dicotyledons can be found in this paper, with emphasis on new information published in the last decade, focusing on the recent advances in molecular taxonomy.
Abstract: This latest revision of my classification and geography of the Dicotyledons replaces my 1992 (Bot. Rev. [Lancaster] 58(3): 225–348) review and is necessitated by the plethora of new information that has become available about the classification of the Angiospermae, especially in the currently popular approaches of cladistic, particulate, and molecular taxonomy. This review attempts to bring up-to-date our knowledge of the dicotyledons, with emphasis on new information published in the last decade. Nearly 600 such recent books, monographs, and other botanical articles are cited in the introduction, listed primarily by the botanical discipline they represent, and in the explanation of the classification. More than 2,000 additional works are listed in the “Literature Cited” section. The numerous changes in the classification created by this new information are listed by subclass and superorder, with pertinent references. A new phylogenetic “shrub” replaces earlier versions and attempts to indicate visually relative sizes and relationships among the superorders, orders, and suborders, with all of these divided into 10 subclasses. One table includes a statistical summary of all known and generally accepted flowering-plant taxa: approximately 257,400 species in 13,678 genera, 389 subfamilies in 490 families, and 756 subfamilies and undivided families in 10 subclasses, 31 superorders, 73 orders, and 64 suborders of Angiospermae. Figures for the dicotyledons are 199,500 species in 10,900 genera, 307 subfamilies in 376 families, and 586 subfamilies and undivided families in 7 subclasses, 22 superorders, 49 orders, and 48 suborders. Three other tables summarize the known indigenous distribution of the families and subfamilies of dicotyledons around the world (the monocotyledons are treated elsewhere). The synopsis lists the dicotyledonous taxa from the subclass down to the subfamily (and in Asteraceae down to the tribe), with indications of the degree of confidence I place in the circumscription and placement of each category above the subfamily, the best available estimates of the number of genera and species for each category, and the known indigenous distribution of each subfamily and family. Table V lists the geographical abbreviations used in the synopsis. The extensive bibliography of pertinent literature on which I have based my decisions should be helpful to persons interested in the classification of the dicotyledons.

137 citations

Journal ArticleDOI
TL;DR: The stratigraphic trend in cuticle types supports the concept that the subclass Magnoliidae includes the most primitive living angiosperms, but it also suggests that the uniformly paracytic stomatal pattern characteristic of Magnoliales may actually be derived from the variable condition found in Zone I leaves.
Abstract: Studies of angiosperm leaf cuticles from the Lower Cretaceous Potomac Group reinforce previous evidence for a Cretaceous adaptive radiation of the flowering plants and suggest unsuspected trends in the evolution of stomata and trichomes. Early Potomac Group angiosperm leaf cuticles (Zone I of Brenner or Aptian?) show little interspecific structural diversity, particularly in stomatal organization. All species conform to the same highly plastic pattern of variation in subsidiary cell arrangement, in which the stomata on a single leaf conform to several types, including paracytic, hemiparacytic, anomocytic, laterocytic, and weakly cyclocytic. Several species resemble extant Chloranthaceae and Illiciales, but none represents a modem family. Later leaves (Subzone 11-B of Brenner, or Albian) exhibit greater interspecific structural diversity, particularly in stomatal organization. Three new patterns of variation in subsidiary cell arrangement are present in addition to the older one and each has a subset of the variation present in the older pattern. Cuticular anatomy is consistent with proposed leaf affinities to Platanaceae and Rosidae. The stratigraphic trend in cuticle types supports the concept that the subclass Magnoliidae includes the most primitive living angiosperms. However, it also suggests that the uniformly paracytic stomatal pattern characteristic of Magnoliales, generally considered primitive for the flowering plants, may actually be derived from the variable condition found in Zone I leaves.

116 citations

Journal ArticleDOI
TL;DR: Analysis of character evolution suggests that the ancestral condition of angiosperms can be described as anomo-stephanocytic, a system in which complexes lacking subdidiaries (anomocytic) intergrade with those having weakly differentiated subsidiaries arranged in a rosette (stepanocytic).
Abstract: Stomatal architecture—the number, form, and arrangement of specialized epidermal cells associated with stomatal guard cells—of 46 species of basal angiosperms representing all ANITA grade families and Chloranthaceae was investigated. Leaf clearings and cuticular preparations were examined with light microscopy, and a sample of 100 stomata from each specimen was coded for stomatal type and five other characters contributing to stomatal architecture. New stomatal types were defined, and many species were examined and illustrated for the first time. Character evolution was examined in light of the ANITA hypothesis using MacClade software. Analysis of character evolution, along with other evidence from this study and evidence from the literature on fossil angiosperms and other seed plant lineages, suggests that the ancestral condition of angiosperms can be described as anomo-stephanocytic, a system in which complexes lacking subdidiaries (anomocytic) intergrade with those having weakly differentiated subsidiaries arranged in a rosette (stephanocytic). From this ancestral condition, tangential divisions of contact cells led to the profusion of different types seen in early fossil angiosperms and Amborellaceae, Austrobaileyales, and derived Chloranthaceae, while the state in Nymphaeales is little modified. Formation of new, derived types by tangential division appears to be a recurrent theme in seed plant evolution.

114 citations