H. von Mohl on the Formation of Gum^Tragacanth. 169 



a swelling- up in a gelatinous form, terminating in their dissolu- 

 tion, being a very ordinary phenomenon in the families of Palmel- 

 lacese, Chroococcacese, and Nostochinese ; that analogous changes 

 of the cell-coats occur in Hydrodictyon and Botrydium ; and that 

 the gelatinous softening of the membrane of the parent-cells of 

 pollen-grains also stands in connexion with their subsequent solu- 

 tion. In like manner I have satisfied myself that the abundant 

 ' intercellular substance^ in the albumen of many Leguminosse, 

 such as Gleditschia and Sophora, depends on an exactly analogous 

 process, on a conversion of the outer laminae of the cell-walls 

 into a homogeneous jelly, in which latter an indication of the 

 primary membrane may often be detected for a long time, till 

 at length it vanishes, and leaves no trace. I have also no 

 doubt that the formation of the 'intercellular substance' of the 

 Fucoids, of Chondrus crispus, &c., depends upon exactly analo- 

 gous processes. We have therefore to regard the formation 

 of gum-tragacanth as a special example of a widely diffused 

 disorganization-process of cell-membrane, which proceeds from 

 without inwards, sometimes affecting the whole cell-wall, some- 

 times only the outer laminae, and terminates in the conversion 

 of the membrane into a more or less soluble jelly. On the other 

 hand, it appears to me less proper to draw a parallel, with 

 linger, between the formation of gum-tragacanth and the form- 

 ation of the secondary and tertiary gelatinous cell-membranes, 

 such as occur in the seed-coats of Cydonia, Linum, Collomia, 

 Ruellia, &c. ; at all events, it is not known to me that these 

 exist in the condition of cellulose-membrane previously to the 

 period in which they are found with the character of gelatinous 

 pellicles. 



Tubingen, Dec. 1856. 



[Note of Translator. — With regard to the remarks in the last paragraph, 

 we find the * swelhng-up' coats of the hairs of Collomia, Ruellia, &c., 

 to be the metamorphosed outer membranes, which take a violet colour 

 with sulphuric acid and iodine when dissolved into a mere jelly, while the 

 spiral fibres or rings (secondary deposits) are colom-ed yellow. Hence we 

 regard these structures as parallels of the cell-membrane of tragacanth. 

 The author's view of the structure of the horny thallus of Chondrus is 

 entirely confirmed by our own examinations of the tissue in various stages 

 of development. — A. H.] 



