55 



The septa of the parenchymatous cells of Eriophorum va- 

 ginatum in full-grown specimens are generally very thick to- 

 wards autumn, but at the extremities of the rays of this ra- 

 diate cellular tissue, which form the oblique septa in the air- 

 ducts of this plant, other distinct expansions are found, con- 

 necting the extremities of the rays* ; and a number of simple 

 and ramified dotted ducts also occur in these, by which the 

 communication in the adjacent cells is facilitated. The forms 

 of this radiate tissue, which originate from these expansions 

 of the radial extremities, are among the most interesting 

 hitherto observed. 



Thickened parenchymatous cells occur even in the interior 

 of the soft substance of the petals, and they are very abun- 

 dant in dots and are frequently very irregularly formed, for 

 instance, in Magnolia grandiflora. 



Similar cells with thick walls, only somewhat elongated, were 

 found by M. Unger at the margins of the ligneous bundles of 

 Helosis and Langsdorffia; he calls them prosenchymatous cells, 

 yet I think that they are only protended thick-sided cells of 

 the parenchyma, similar in every respect to those which occur 

 at the sides of the ligneous bundles of common Monocotyle- 

 dons : I do not however recognise them as cells of the liber. 

 In Langsdorffia five to eight only of such thick-sided cells are 

 united into a bundle, but in Helosis they are situated in the 

 form of a half-moon at the inner sides of the bundles, while in 

 Langsdorffia they are abundantly diffused through the entire 

 stock, both within and at the exterior of the vascular circle. 

 M. Unger supposes that for this reason a similarity in the struc- 

 ture of the stem of Helosis and Langsdorffia with that of the 

 stems of ferns may be inferred. I have also found in the stem 

 of Pandanus anastomosing ligneous bundles peculiar to these 

 parasites. 



The occurrence of spiral tubes in all true parasites is at pre- 

 sent well ascertained ; and M. Unger has also convinced him- 

 self of their occurrence. The spiral tubes of the Rhizantheae 

 belong mostly to the reticulated and porous, and have short 

 articulations. 



I have published a memoir on the epidermis of vegetables f, 



* Neues System der Pflanzen-Physiologie, Berlin, 1837, i. p. 5. 

 t Wiegmann's Archiv, 1837, p. 211228. 

 D2 



