820 SUMMARY OF CURRENT RESEARCHES RELATING TO 



surfaces of the lamina of the petals, but not in the claw. The author 

 believes it to differ altogether from ordinary starch in its physio- 

 logical function in the life of the plant, being simply a secondary 

 product of excretion. It is capable of being formed in darkness. 



Occurrence of the Elements of Milk-sugar in Plants.* — M. A. 

 Miintz identifies the substance contained in gum-arabic, hitherto 

 known as arabinosc, with galactose, agreeing with this substance in 

 its specific power of rotation (+ 80"), its fusing-point (170° C), and 

 its property of yiolding on oxidation a largo quantity of mucic acid. 

 The same was the case with all the gums examined which were 

 obtained from fruits or the trunks of trees, or by extracting from 

 various plants, or which are sold in commerce. 



Reactions of three Red Vegetable Pigments.! — Herren T. F. 

 Hanausek and R. Czermak describe the reactions of the pigments of 

 the hollyhock, bilberry, and Chica. The pigments of the first- 

 named two plants become light red in acids, green in alkalies, 

 Indian-ink tint in borax, and arc destroyed by calcium chloride 

 and hydrogen. Chica-red is obtained by boiling the leaves of 

 Bignonia Chica and B. tinctoria, appearing as a cinnabar-red 

 deposit, when the bark of a tree called "aryana" is added to the 

 water. Cotton is coloured a beautiful orange-red by this pigment. 

 Acids change the red into oil- or wine-yellow, caustic potash or soda 

 make the hyacinth-red alcoholic solution muddy ; iron-sulphato and 

 chloride turn it brown, hydrogen and calcium chloride remove the 

 colour entirely, magnesium carbonate partially ; sugar-of-lead turns it 

 flesh-coloured. Treated with sulphurous acid, Chica-red becomes at 

 first chrome-yellow, then somewhat turbid with development of sul- 

 phuretted hydrogen. If the solution is filtered, it fluoresces red- 

 yellow, and deposits after a time a yellow sediment. 



Exoderm.J — M. P. Vuillemin proposes to define more accurately 

 than hitherto the term exoderm, corresponding to the endoderm of 

 Van Tiegkem, Its definition must be anatomical and morphological 

 rather than physiological. It is the outermost layer of the bark ; and, 

 like the endoderm, its functions may vary greatly under different cir- 

 cumstances, although it may also be the seat of special formations. 

 It varies also in being more or less sharply differentiated from the 

 subjacent layers. 



Pericycle of Caryophyllacese.§ — According to M. P. Vuillemin, 

 the structure of the pericycle is very constant throughout the Caryo- 

 phyllaccse. It usually consists of two zones : — (1) An outer scleren- 

 chymatous zone, the elements of which are sometimes fibres with 

 scarcely any cavity, sometimes cells with thin but lignified walls ; 

 (2) an inner parenchymatous zone, the outermost layer of which 



* Comptes Rendus, cii. (1886) pp. 624-7. 



t Zeitschr. f. Landwirlh. Gewerbe, 1885, pp. 131-3. SceBot. Central bl., xxv. 

 (18S6) p. 254. 



: Bull. Soc. Bi.t. France, xxxiii. (1886) pp. 80-1. 

 § Ibid., xxxii. (1885) pp. 275-82. 



