Meyen's Report for 1839 on Physiological Botany. 331 



which are contained in the parenchym surrounding the no- 

 dules. The tubers of several South American Ophrydeee when 

 dried have the appearance of a bag filled with pebbles, or as 

 if the epidermis had contracted over the hard interior body. 

 A transverse section of a fresh root of Satyrium pallidum ex- 

 plains the above appearance : the hard nodules, as transparent 

 as water, are mingled together with the soft parenchym, and 

 they are twenty times as large as the neighbouring cells. 

 These nodules are easily separable, and appear as hard as horn; 

 on section they appear perfectly homogeneous ; cold water has 

 scarcely any effect upon them, but in hot water they become 

 tumid, and are partly changed into a transparent jelly. An 

 aqueous solution of iodine has no visible effect on them in their 

 natural state. On charring some slices of salep. Dr. Lindley 

 found that these apparently homogeneous nodules consisted 

 of very minute cells, filled with a substance of the same re- 

 fractive power as themselves. Finally, Dr. Lindley declares, 

 that the en'or of considering salep to consist chiefly of starch, 

 arose from the mode of preparation. The tubers of the 

 Orchidea are first parboiled and then dried ; by this means 

 the starch which surrounds the nodules is dissolved, and on 

 drying is precipitated upon their surface, and hence they be- 

 come blue when treated with iodine. Dr. Lindley's state- 

 ments with regard to the structure of these roots are so very 

 peculiar, that I felt it necessary to examine the subject my- 

 self. The examination of two kinds of salep-roots, as also 

 comparative observations of a fresh tuber of Orchis milita- 

 ris, soon showed, that in the structure of the Orchideous 

 roots there is nothing differing from the general rule. Those 

 hard horny nodules are nothing more than hardened masses 

 of tragacanth gum which fill the individual cells, which in this 

 case are often of a large size ; Berzelius had already referred 

 the sale[) mucilage to tragacanth gum, and in different Orchi- 

 dea this substance appears to differ only according to its 

 several degi'ces of hardness. In the cells of the roots of Or- 

 chidece is universally observed the presence of a cellular nu- 

 cleus, and round this is formed a thick mucilaginous mass, as 

 also a greater or smaller number of minute, nearly round glo- 

 bules, which are generally coloured yellowish brown by iodine, 

 but sometimes bluish. The mass of this thick mucilage, as 

 also that of the globules, continually increases within the cells, 

 and in those tubers which can be advantageously used for the 

 preparation of salep, the contents of the single, often very 

 large, cells assume a gelatinous consistency, and on drying 

 become as hard as horn, and may then easily be mistaken for 

 nodules. I have now before me some sections of dried sdcp- 



