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Summaryin Vitis (grape) calcium oxalate crystals form in a needlelike morphology unique to plants, presenting an intriguing system of biological control over mineral formation. Crystals develop within an organic matrix which appears to provide control over the sites and forms of crystal deposition; however, little is known about the chemical nature of the matrix. A procedure has been developed to isolate crystals along with their associated intravecuolar matrix from leaves of grape, and studies have been initiated into the chemical composition of the matrix by characterizing elemental content, carbohydrates, and protein. The isolated matrix consisted of two structural phases, membrane chambers enclosing developing crystals, and a water-soluble phase surrounding the crystal chambers. Elemental analysis detected substantial calcium and potassium, as well as some iron in the water-soluble phase. Analysis of the water-soluble matrix by GC-MS showed that it contained an unusual polymer with novel glucuronic acid linkages. In addition, linkage analysis indicated 6-linked arabinans, arabinogalactan, and various mannosyl units typical of complex carbohydrates of Nlinked glycoproteins. SDS-PAGE analysis of the wetersoluble matrix and crystal chambers showed that each had distinct banding profiles in silver-stained gels, with prominent 60 and 70 kOa polypeptides in crystal chamber extracts. Demineralization studies provided direct evidence that the isolated matrix promotes crystal nucleation. The findings about the organic matrix associated with calcium oxalate crystals in grape are discussed in relation to crystal nucleation and growth and features shared with animal and microbial biomineralization systems.

The structure of Euglena granulata and Chlamydomonas eugametos has been studied using polarization and electron microscopy, cinematography, and chemical extraction procedures, with the main focus on the structure of the eyespot.The 50-60 granules which form the extrachloroplastic eyespot of E. granulata are large bodies, up to 1200 mμ in diameter. They are found in the cytoplasm near the base of the reservoir and are associated with the parabasal body which contains a large crystal. The eyespot granules are contained within membranes having a unit membrane structure; 2 or 3 are usually present in a single eyespot packet; microtubules are also contained within the packet. The eyespot granules have the structure of a positive spherite and clearly exhibit birefringence; this structure is modified by fixation.The granules of the chloroplastic eyespot of C. eugametos are about 75 mμ in diameter and are contained within the chloroplast in an ordered array. Occasionally, the eyespot contains elongate or helical bodies mixed with the granules. Extraction with organic solvents caused the removal of materials which formed the eyespot granules as well as that of the osmophilic globules in the chloroplasts.Several hypotheses which concern the function of the eyespots in these and other species are discussed in the light of our results. the possible origin and demise of the eyespot granules are also discussed.

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