1993. On the relationship of the Apocynaceae and Periplocaceae. -Grana Suppl. 2: 3-20.It is generally agreed that the Periplocaceae arose from apocynaceous ancestors. Whether these ancestors were from the Plumerioideae, Cerberoideae or Apocynoideae has long been in dispute. This investigation is a comparative study of the pollen morphology and floral structure of selected genera of Apocynaceae and Periplocaceae. The examinded genera of the Plumerioideae and the Cerberoideae have 3-colporate, smooth to sculptured pollen grains. In the Apocynoideae there are single, smooth, 2-3-porate pollen grains or 3to multiporate grains loosely united in tetrads of variable size and shape. The exine consists of an outer thick, homogeneous stratum subtended by a very thin, granular-fibrillar stratum, and globules; the internal septa are double-layered due to partial fusion of the tecta of the individual grains. The genera of Periplocaceae have pollen grains united in elongated, rhomboidal to rounded, or tetrahedral and decussate tetrads with few to many pores, pairwise, opposite or irregularly arranged. The exine consists of a homogeneous outer stratum and a thin granular stratum below. The internal walls (septa) are relatively thin, and perforate. Heniidesnrrrs has an aggregation (massula) of elongated tetrads with indistinct pores. The exine is divided into a compact outer stratum and an inner, fairly thick, granular stratum. The inner walls (septa) are thin, granular, and non-perforated. Trends in floral structure center around increasing precision of the pollination mechanism for transport of pollen en masse. In the Apocynaceae this is mainly effected by the androceum and gynoecium. In the Periplocaceae the corona is also incorporated. Porate tetrads are correlated to a large extent with the advent of translators. Style-head secretions evolve from foamy adhesive for the transport of single pollen grains in the Apocynaceae to firm translators transporting pollen tetrads in the Periplocaceae and in Forsferonio, Apocjrirrm. Poocjirrini and Troclruniririon. The latter three genera are so similar in all respects that recognition of more than one genus seems unjustified. With special reference to pollen morphology a possible trend of evolution is postulated from taxa with single, 3-colporate grains to 3-porate grains and from taxa with pollen united in tetrads with compact inner walls as in the Apocynoideae, to taxa of the Periplocaceae with tetrads perforated septa and to taxa with pollen (tetrads) in masses. The Periplocaceae appear unrelated to the Plumerioideae and the Cerberoideae. The similarity between tetrads of A~OCJIIICIII s.1. and Periplocaceae is here regarded as parallel evolution within two closely related lineages. Siwerr Nilssori, Elisobeth Grofsrroin, Poljriologicnl lnborofory, Swedish hfirseruii of Notrrrnl Histov, S-I04 05 Stocklrolin, Sweden; hfory E. Bidress, Universitiit Ziiricli, Botanisclrer Gorteri wid Irisrirrrr fiir Sjstenidsclie Buronik, Zollikerstrosse 107. CH-SO08 Ziiricli. Switzerloird.

The external morphology, internal structure and stainability for protein of orbicules in Betitla pertdula are examined by SEM and TEM. The pollen and the orbicule walls stain moderately for protein. The protein is localized mainly at the pollen aperture, in a thin layer betneen the exine and the intine and in the core and on the surface of the orbicules. The nitrocellulose membrane test indicates possible allergenicity of the orbicules as well as of the pollen. Since the orbicules of Befirla peiidula are 2-4 pm in diameter, they can pass through the bronchiole of the lungs and cause bronchial asthma. Orbicules have been recognized since 1865 by Rosanoff, who described a membrane with granules around the pollinia in the Mimosaceae. Ubisch (1927) and Kosmath (1927) published lists of different species that contain tapetal cells with orbicules on their surface. These early studies were followed by several others which were based solely on light microscopy investigations (for detailed review, see Banerjee 1967 andRaj &.Later studies using SEM andTEM were published on the morphology and ontogeny of orbicules (Ubisch bodies), e.g., Rowley (1962Rowley ( , 1963 To our knowledge, there is no information published on the morphology, ontogeny and histochemistry of orbicules in Befirla.The allergenicity of Befirla pollen is well documented (Wihl et al. 1988. However the possible allergenic effects of the orbicules in Betrrla have not yet been investigated. Takahashi et a1 (1991, 1995) demonstrated the presence of small particles with Cry j allergen activity together with intact, airborne Cryptoiseria japonica pollen *grains during the pollen season. The sites of C r y j I were found to be on the pollen exine and on the orbicule walls (MikiHirosige et al. 1994 andTakahashi et al. 1992).In the present study we describe the morphology and ultrastructure of orbicules in Betrrla pendirln. The allergenic effects of Betirla pollen and orbicules are also tested by the immunoblotting method. MATERIAL AND METHODSThe material for this study was collected during the period 1989-1993 from a Berula tree growing close to the Palynological Laboratory, Stockholm.For SEM preparations, fresh anthers mere dehydrated in an acetone series. Anthers were opened longitudinally and mounted on a stub. They were coated with gold for 3 minutes and examined with a Jeol JSM 6300 microscope.For TEhl preparations, anthers \\ere futed in 2% glutaraldehyde (GA) in 0.05 M Nacacodylate buffer, pH 7.4 at room temp. for 24 hours, postfixed with 0~01, then dehydrated in an acetone series, embedded in Spurr's medium (Spurr 1969) and sectioned. Ultrathin sections were stained with 1% aqueous uranyl acetate for 5 min, washed with distilled water, and floated on lead citrate stain for 5 minutes in order to improve the general contrast. Stain for protein: Sections on gold grids were stained with 5% phosphotungstic acid (FTA) in 10% acetone for 15min (Benedetti & Bertolini 1963, Marinozzi 1968. Aeroallergen immunoblotting procedureSamples collected on Burkard tapes w...

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