Studia Forestalia Suecica

ODC 164.5: 174.7 Pinus sylvestris + I68 164.5 T h e ultra.structure of the different cell types in mature needles o f pine (Pinus silvestris L.) is described. The epidermal cells are protoplasma-free with prominent secondary a~alls. The sunken guard cells have chloroplasts o f a simple structure and many mitochondria. A hypodermal layer is formed by living vacuolated fiber cells. The mesophyll cells, which have tanniniferous vacuoles, are rich in chloroplasts and mitochondria and contain microbodies. T h e resin ducts have secretory cells with a unique kind o f plastid, apparently engaged in resin production. The endodermal cells are characterized by strongly osmiophilic globules in the vacuoles. The transfusion tissue consists of thin-walled deformed traclzeids with bordered pits and parenchyma cells with tanniniferous vacuoles of different types. Like endodermal cells these parenchyma cells have simple anzocboid chloroplasts. Albun~inous cells with numerozts small tannin-free vacuoles and localized w~all thickenings traversed by bunches of plasmodesmuta are found on the outer side o f each bundle. The adaxial xylem contains protoxylem rracheids with spiral wall thickenings and metasylem elements with evenly thickened walls. A f~tsiform cambium is inserted between the xylem and the phloem. T h e sieve cells have unique multilayered secondary walls. Plastids in these cells contain clusters of protein fibrils which become released into the protoplast. Ms. recieved 1973-05 15