984 SUMMARY OF CUURENT RESEAROHES RELATING TO 



March, is only true to a limited extent for Gymnosperms, with the excep- 

 tion of the (^uctacciD. 



The rescrve-matcriiils in evergreen leaves consist of starch, fatty oil, 

 and tannin ; the latter may be alone or may be accomjjanied by either of 

 tlie otliers. Starch and tannin, however, are seldom found in the same 

 cell ; there appears to be a certain alternative relationship between tliem. 

 Details arc given with respect to the special tissue in the leaf in which 

 the tannin is mostly found. 



Under the head of both Gymnosperms and Dicotyledones the details 

 of the observations on a number of species are given. 



Glucose as a Reserve-material in Woody Plants.* — Very few obser- 

 vations have hitherto been made on the occurrence of glucose as a reserve- 

 material. Dr. A. Fischer states that it is of very common occurrence 

 in woody Angiosperms. He finds it especially in the cells of dead 

 tissues from which the protoplasm has disappeared. He never met with 

 it in the living elements of the wood, the medullary rays, or the 

 ])arcnchyma of the wood, in which other non-nitrogenous reserve- 

 substances (oil, starch, and tannin) are stored up. The distribution in 

 the dead elements of the bark, the pith, and the wood, varies very greatly 

 in diifcreut trees. The test used for the presence of glucose was the 

 ordinary one of the reduction of oxide of copper. 



Colourless Oil-plastids in Potamog^eton.f — Herr A. N. Lundstroni 

 observes that the young leaves and stipules of many species of Potamo- 

 geton exhibit a shining surface, which renders them completely dry even 

 when immersed in water. This is due to large drops of oil in the 

 epidermal cells. The author states that the formation of these oil-drops 

 is connected with certain definite minute bodies contained in them, which 

 he compares with Schimiier's starch-generators or leucoplastids, and 

 terms " oil-plastids," They are rod-shaped, from 2-9 /x in length, and 

 • 5 /u. in breadth ; there is sometimes only one, sometimes two or three 

 are associated with each droj) of oil. In living cells they are in a constant 

 oscillating motion. They are not situated in the vacuoles, but in the 

 parietal protoplasm, and are independent of the nucleus. They often 

 disappear very rapidly out of the cells, and are certainly not the direct 

 result of assimilation, being formed long before the chloroi)hyll-grains. 



Substance of which Gum-arabic is formed.| — Herr F. v. Hohnol 

 has determined, by examination of a branch of Acacia Vereh to which 

 was attached a large lump of gum, that it cannot have been formed, as 

 is the ease with tragacanth and some other gums, by disorganization 

 of the substance of the cell- walls, but that it belongs to the class of gums 

 foiTUcd by modification of the cell-contents. 



Tannin and its connection with Metastasis.§ — Herr H. Moeller 

 maintains tliat tannin arises in the plant as an oxidation jiroduct in the 

 transformation of starch ; that starch unites with tannin to form a 

 glucoside, possibly grape-sugar or amylodcxtrin ; and that this glucosido 

 splits up easily into tannin and sugar, starch, or cellulose. Tannin is 



* Bot. Ztg., xlvi. (1888) pp. 405-17. 



+ SB. Natiu-v. Studentsallsk Upsala, Oct. 20, 1887. See Bot. Centralbl., xxxv. 

 (1888) p. 177. X Bor. Deutsdi. Bot. Ge.scll., vi. (1888) pp. 150-9. 



§ 'Ucb. d. Voikoninun d. (Jcrbsaiire u. ilirc Bcdeutuug f. d. Stoffwecbscl,' 

 Berlin, 1888. See But. Ceutralbl , xxxv. (1888) p. 266. 



