ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 587 



tissues of the Hyijericacefe abound. He concludes, (1) that the view 

 advocated by Link, Martinet, and de Bary of the lysigenous origin 

 of the reservoirs of ethereal oil in these plants is the correct one. 

 (2) That there exists in many parts of the plants a series of ducts 

 or passages differing only slightly from these reservoirs ; the differences 

 being that they are not globular and isolated, but are generally 

 connected more or less intimately with each other, and that their 

 secretion is not a clear ethereal oil, but a viscid or resinous liquid, the 

 points of agreement being those connected with their development and 

 function. (3) In some species at least there is also a series of 

 schizogenous ducts confined to certain portions of the phloem. (4) 

 There are certain dark glands described in the paper which are in 

 intimate relationship with the fibrovascular system. (5) The formation 

 of resin and kindred secretions in these plants is confined to the parts 

 where metabolism is active, and where there is a primary meristera. 

 All such parts give evidence of such formation with the exception of 

 the roots. 



Tracheids of Gymnosperms.* — M. Scheit describes the group of 

 peculiarly thickened cells (the tracheid-seam of de Bary) found in the 

 leaves of conifers on both sides of the vascular bundle, at one time 

 considered as a part of the transfusion tissue. In the living condi- 

 tion these are filled with water or aqueous vapour, but not with air, 

 as is shown by placing twigs of Pinus Pumilio in turpentine oil. 

 The cells themselves are true tracheids, exhibiting sometimes a reti- 

 culate thickening, sometimes bordered pits. These " seams " occur 

 not only in conifers, but also in the other orders of Gymnosperms, 

 the Gnetacese and Cycadefe, where they consist of very small and few 

 cells, greatly resembling the adjoining parenchymatous cells in the 

 mode of thickening. They are therefore an anatomical characteristic 

 of Gymnosperms generally. 



The variation in the mode of thickening in these cells corresi)onds 

 to their function as a protection against the pressure of neighbour- 

 ing turgid cells. Where the " seams " are separated from the 

 parenchyma of the leaf by thickened sheaths, the tracheids have only 

 bordered pits ; when they are in immediate contact with the paren- 

 chyma, they are thickened reticulately. The extent of development 

 of these " seams " depends on the intensity of transpiration of the 

 species. In Pinus Pinea, which spreads its crown as wide as pos- 

 sible beneath the clear sky of Italy, they arc very strongly developed ; 

 while in Pinus Strobus, which prefers moist climates and thrives best 

 in bogs, they are but very feebly developed. 



Apparatus in Leaves for Reflecting Light.f — 0. Penzig has ex- 

 amined the structure of the clusters of crystals found in the leaves of 

 the Aurantiacofe, clothed with cellulose, and attached to the wall of 

 the mother-cell — the idioblasts of Ptitzer ; and believes they arc 



• Jenaieche Zcitschr. f. Naturwiae., ix. (1883) (1 iil.). See But. Ztg., xlii 

 (1884) i>. 74. 



t Atti Soc. Nat. <li Modoiifi, i. (ISK.'?) (1 jil.). Soe But. Ontnilbl., xvii. (1SH4) 

 p. :^^^■^. 



2 i; 2 



