268 SUMMARY OF CUEKENT RESEAEOHES RELATING TO 



give off carbonic acid. Drying oils are known to absorb oxygen even 

 in tbe dark; vv^hen mixed with chlorophyll the oil becomes nearly 

 inoxidizable in the dark, but its oxidation in the light is increased 

 by the presence of chlorophyll. 



Contents of Sieve-tubes.* — Dr. A. Fischer states that the 

 collection of mucilage seen beneath the sieve-plate in sections of sieve- 

 tubes, and known as " Schlauchkopf," does not occur in the tubes in the 

 uninjured plate, but is the result of injury. No trace of this structure 

 is apparent if the plant is first boiled for from two to five minutes, by 

 which means the contents of the sieve-tubes are coagulated. When 

 treated in this way, the sieve-tubes of Cucurhita are seen to be com- 

 pletely filled by a finely turbid granular mass, while a parietal layer of 

 protoplasm can be demonstrated by staining ; it sometimes contains 

 drops of mucilage. The author considers that in the uninjured state 

 the sieve-tubes of Cucurbita contain a clear thin mucilaginous sap ; 

 when the tubes are cut, a portion of this sap is pressed out; the 

 sieve-plate acts as a filter and keeps back the denser part, which then 

 forms the " Schlauchkopf." 



Colouring Matters of Plants.f — According to Sig. P. Baccarini 

 the red and yellovr colour of plants is not always due to the presence 

 of chromoblasts. Where this is the case, the originally round 

 chromoblasts frequently lose their form in consequence of crystalliza- 

 tion, as in the fruits of Eugenia hahiensis and the flower-buds of 

 Bignonia venusta ; while in others the form is changed by the forma- 

 tion of a vacuole in their interior, as in the flowers of Tecoma capensis, 

 Tritomia uvaria, and Aloe socotrina. 



The inner perianth-leaves of Chamsedorea elegans display before 

 blossoming a chestnut-brown colouring due to amorphous masses of a 

 non-protoplasmic character within the cells. In the unripe fruits of 

 EucTiylsena tomentosa there are, in the parenchymatous cells, more or 

 less rounded grains of chlorophyll, usually with a vacuole in the 

 middle ; as these capsules disappear the vacuole swells, and the 

 contents become yellow or bright red from the formation of a soluble 

 pigment. A similar soluble yellow pigment is found in the fruits of 

 Mivina laevis, and the flowers of Calceolaria amplexicaulis and Buddleya 

 madagascariensis. The yellow colour of the flesh of the fruit of 

 Eugenia hahiensis is caused by tabular chromoblasts within the cells, 

 probably derivatives of chlorophyll. 



Tbe roots of EcJiium plantagineum are coloured in patches on the 

 surface from amorphous masses of protoplasm permeated by a pigment. 

 In the flower-buds of Bignonia venusta, alcohol causes a precipitation 

 of sphero-crystals, which the author regards as a calcium phosphate. 



Pigment-bodies in Neottia nidus-avis.| — Herr 0. Lindt opposes 

 the view of Wiesner that chlorophyll exists in the cells of this 



* Ber. Deutsch. Bot. Gesell., iii. (1885) pp. 230-9. Of. this Journal, v. 

 (1885) pp. 477, 1020. 



t Ann. Istit. Bot. Koma, ii. (1885) 23 pp. (1 pi.). See Oester. Bot. Zeitschr., 

 XXXV. (1885) p. 439. 



X Bot. Ztg., xliii. (1885) pp. 825-34. 



