STRUCTURE.] FIBKOCELLULAR TISSUE. 51 



forms of tissue in which the bladders taper to each end, and 

 consequently overlap each other at their extremities. 



Meyen has Merenchym, for ellipsoidal and spheroidal cells ; 

 Parenchym for angular cells ; and Prosenchym as above 

 described. 



FIBRO-CELLULAR TISSUE is thafc in which the sides are 

 composed either of membrane and fibre together, or of fibre 

 only. Link calls all such tissue spiroid. 



The first observation of this kind with which I am 

 acquainted is that of Moldenhauer, who, in 1779, described 

 the leaves of Sphagnum as marked by fibres twisted spirally 

 (fig. 3. #, p. 26.) In November, 1827, 1 described the tissue 

 of Maurandya Barclayana as consisting of bladders formed 

 of spiral threads crossing each other, interlaced from the base 

 to the apex, and connected by a membrane. A few other 

 solitary cases of this kind of tissue had subsequently been 

 observed when the investigations of a modern anatomist 

 suddenly threw an entirely new light upon the subject. 



Instead of being very rare, cellular tissue of this kind 

 appears to be quite common ; it has been already mentioned 

 as existing in the leaves of Sphagnum ; it is also found in 

 the pith of Rubus odoratus. I originally discovered it in the 

 parenchym of the leaves of Oncidium altissimum, and in the 

 coat of various seeds. Mr. Griffith detected it abundantly 

 in the aerial roots of Orchids, where in fact it is extremely 

 common, and Purkinje has shown, by a series of excellent 

 observations and drawings, that it constitutes the lining of 

 the valves of almost all anthers. 



Schleiden would seem to regard the spiral condition of the 

 interior of cells as a universal fact. But, although we know of 

 nothing to support this strong opinion, which seems to 

 result from hypothetical considerations, his statements 

 respecting some instances, in which it certainly occurs, are 

 interesting. After adverting to the spiral structure known 

 to exist in the reproductive organs of Liverworts and Scale- 

 Mosses, he shows that it is not less strikingly developed in 

 the organs of vegetation of Liverworts (Marchantiacese.) 

 The parenchym of the leaf in Marchantia polymorpha and 



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