Bd. XCIII. No. 20. XXIV. Jahrgang. 



Botanisches Centralblatt. 



Referirendes Organ 



der 



Association Internationale des Botanistes 



für das Gesammtgebiet der Botanik. 



Herausgegeben unter der Leitung 

 des Präsidenten : des Vice-Präsidenten : des Secretärs : 



Prof. Dr. K. Goebei. Prof. Dr. F. 0. Bower. Dr. J. P. Lotsy. 



und der Redactions-Commissions-Mitglieder : 



Prof. Dr. Ch. Flahault und Dr. Wm. Trelease. 



von zahlreichen Specialredacteuren in den verschiedenen Ländern. 

 Dr. J. P. Lotsy, Chefredacteur. 



No. 46. 



Abonnement für das halbe Jahr 14 Mark 



durch alle Buchhandlungen und Postanstalten. 



1903. 



Alle für die Redaction bestimmten Sendungen sind zu richten an Herrn 

 Dr. J. P. LOTSY, Chefredacteur, Leiden (Holland), Oude Rijn 33 a. 



Fritsch, f. E. , „Recent Discoveries of Caoutchouc 

 in Plants." (The New Phytologist. 1903. p. 25—30.) 



Radlkofer described threads of semi-solid caoutchouc in Pcira- 

 meria vnlneraria ; and it has also been found in Encommia iilmoides, 

 Wimmeria cyclocarpa and Plagiopteron, Salacia micrantha, and 3 stems 

 of Hippocrateaceae and in Evonymiis. 



The material constituting these very elastic threads is insoluble in 

 alcohoi, but soluble in ether, benzol or Chloroform. It is doubly 

 refractive in polarised light. The threads take up certain stains readily. 

 On evaperation of the benzol - Solution, a thin, greyish - white elastic 

 film remains, which burns with the small characteristic of burning 

 rubber. The French investigators regard the substance as more of the 

 natura of india rubber. The caoutchouc is contained in laticiferous cells, 

 which are often so long that no terminations have been found in the 

 stem. In Hippocratea ovata the cells were observed in the embryo in 

 the seed, viz, in the cotyledons. They occur in both primary and 

 secondary phloem of the stem, and also in primary cortex ; in 

 Plagiopteron alone are they found in the pith. They are common in 

 phloem and cortex of petiole; in the lamina they are restricted to lower 

 side of the veins. Caoutchouc-cells occur in all parts of the flower. 

 The stage at which the cells begin to appear is arrived at earlier in the 

 growth of some species than in that of others. In some species of 

 Hippocrateaceae and Celastraceae, the caoutchouc-cells are restricted to 

 the axis of the plant, and there only in the secondary cortex. They are 

 developed probably by differentiation and stretching of ordinary parenchy- 

 matous cells, as described by Weiss for Encommia. In their late 

 appearance and their restriction to the axis the unbranched caoutchouc- 

 cells of the Hippocrateaceae and Evonymiis are probably more primitive 

 than those of Encommia. The authorsuggests the probable method of 

 evplution of the branched from the unbranched type. Nothing can be 

 Said as to the function of the caoutchouc-cells until further plants have 

 been investigated. Their semi-solid condition prevents their being 

 regarded as Channels for the conveyance of food. 



VV. C. Worsdell (Kew). 



Botan. Centralbl. Bd. XCIII. 1903 32 



