VEGETABLE ORGANIZATION. 69 



of this description are said to be reticulated or 

 spotted, and, together with those having more 

 regularly formed spiral threads, are very abun- 

 dantly met with in plants belonging to the tribe 

 of Orcliidece. 



It has been much disputed whether the cells 

 of the vegetable texture are closed on all sides, 

 or whether they communicate with one another. 

 Mirbel has given us delineations of what ap- 

 peared to him, when he examined the coats of 

 the cells with the microscope, to be pores and 

 fissures. But subsequent observations have 

 rendered it probable that these appearances 

 arise merely from darker portions of the mem- 

 branes, where opaque particles have been depo- 

 sited in their substance. Fluids gain access 

 into these cells by transuding through the mem- 

 branes which form their sides, and not by any 

 apertures capable of being detected by the 

 highest powers of the microscope. 



If all the cells consist of separate vesicles, 

 as the concurring observations of modern bo- 

 tanists* appear to have satisfactorily established, 

 the partitions which separate them, however thin 

 and delicate, must consist of a double membrane, 

 formed by the adhesion of the coats of the two 

 contiguous vesicles. But as these coats can 



* In particular, Treviranus, Kieser, Link, Du Petit Thouars, 

 PoUini, Amici Dutrochet, and De CandoUe. 



