The halophytic genus Suaeda (Chenopodiaceae) includes species with the C3 and C4 photosynthetic pathways. North American species of this genus were investigated to determine whether C3 and C4 leaf anatomy are consistent within the two sections of Suaeda, Chenopodina and Limbogermen, present on this continent. All species from section Chenopodina were found to possess C3 anatomy, whereas all species from section Limbogermen were found to be C4 species. Characteristics of leaf anatomy and chloroplast ultrastructure are similar to those reported from C3 and C4 species, respectively, from the Eastern Hemisphere. All species from section Limbogermen have the suaedoid type of leaf anatomy, characterized by differentiation of the mesophyll into palisade parenchyma and a chlorenchymatous sheath surrounding central water-storage tissue, as well as leaf carbon isotope ratios (_13C) of above -20. All species from section Chenopodina have austrobassioid leaf anatomy without a chlorenchymatous sheath and _13C values of below -20. According to our literature review, the photosynthetic pathway has now been reported for about half (44) of the Suaeda species worldwide. The C3 and C4 photosynthetic syndromes are with few exceptions distributed along sectional or subsectional lines. These findings throw new light on the infrageneric taxonomy of this genus.

This paper is based on the lecture entitled “Communication Channels Between Cells and Their Origin in Higher Plants” presented by K. E. on 14 May 1984 at the University of California‐Davis as part of the Department of Botany Symposium “Integrating Plant Structure and Function.” This symposium was arranged in connection with the UCD 75th Anniversary Celebration. The main theme of the paper is the developmental relation between the plasmodesmata and the sieve plate pores in the phloem conduits of several dicotyledons. New observations and a review of some pertinent data from the literature are combined.

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Anatomical study of several species of the putatively primitive orchids Apostasia and Neuiviedia was based on specimens of leaves, stems and rootS. Research was carried out in the hope of providing objective information from anatomy towards unravelling the relationships of these plants, and especially towards answering the question of whether extant orchids evolved from these two genera, or from plants like them. The morphology of Apostasia and Neuwiedia has evoked the dogma of primitiveness because of the two or three anthers borne on separate filaments and the free style and stigma which characterize the flowerS. In most other orchids there is only one anther and filaments and styles are fused to form the column (gynostemium). The general anatomical structure of apostasiads shows features present in other orchids; none is restricted to Apostasia and Neuwiedia. Tracheary anatomy, however, shows vessels in roots, but not in any part of the shoot system. Vessel members are characterized by chiefly simple perforation plates in contrast with other orchids where scalariform perforation plates predominate in vessel members of the root. These phenomena, considered from the phylogenetic standpoint, would cast serious doubt on the possibility that plants with scalariform perforation plates, the ancestral, or primitive condition, could have arisen from plants with simple perforation plates, the derived, or advanced condition. On this basis the apostasiads could not have given rise to the di‐ and monandrous orchidS. Of the several suggested origins for orchids, Hypoxidaceae, or plants similar to them, whether in Asparagales, Liliales or Haemadorales of different authors, could have been the progenitors of orchids as a group, including the apostasiadS. Because of the unique combination of floral features in the apostasiads, their predominantly simple perforation plates, and their overall anatomical similarity to orchids in general, it would appear appropriate to consider them as a subfamily, Apostasioideae, of Orchidaceae sensu lato.

A survey of 68 species representing 28 genera in the family Boraginaceae was conducted at the ultrastructural level to determine presence of nuclear crystalloids in sieve elements and occurrence of crystalline structures in chloroplasts of phloem parenchyma cells. Nuclear crystalloids were identified in 55 of the species examined, and 25 of the species contained chloroplast crystals. The nuclear crystals were mainly composed of thin rods densely packed in parallel arrangement. Their sizes, shapes, and numbers varied, but they were basically prismatic or possibly cubical. During maturation, the sieve element nuclei disintegrated and the crystalloids were released into the cell lumen where they remained intact. Loosely arranged paracrystalline components associated with the dense nuclear crystalloids were found only in the genus Amsinckia. Crystalline inclusions in the parenchyma chloroplasts were made up of fibers loosely aligned in a herringbone pattern. The lability of the chloroplast crystals to the proteolytic enzyme, protease, was tested on 10 species, and only Onosma stellulatum Waldst. & Kit. chloroplast crystals were routinely digested. The high percentage of nuclear crystalloids found in this family suggests that these inclusions could be valuable as a systematic character. Key words: sieve elements, nuclear inclusions, plastid crystals, Boraginaceae.