1887.] 



On the Structure of Mucilage Cells. 



353 



I. " On the Structure of the Mucilage Cells of Bleclmum 

 occidentale (L.) and Osmunda regalis (L.)" By ToKUTARO Ito, 

 F.L.S., and Walter Gardiner, M.A. Communicated by 

 Professor M. FOSTER, Sec. U.S. Received May 31, 1887. 



The growing point of many ferns is found to be covered with a 

 slimy mncilage which arises from hairs situated on the palee and the 

 leaves, or where palae are absent on the leaves only. This mucilagin- 

 ous secretion serves a most important physiological function, in that 

 it readily takes up and retains water, and thus keeps the young bud 

 moist, and at the same time tends to prevent too excessive transpira- 

 tion. The cells which secrete the mucilage are large and swollen, 

 and the secretion escapes by the rupturing of the cell wall. We 

 investigated two cases of mucilaginous secretion, viz., Blechnum occi- 

 dentale (L.), where iu each hair only the terminal cell is glandular, and 

 Osmunda regalis (L.), where usually all the cells of the hair are 

 equally endowed with secretory function. We find that the mucilage 

 arises from the protoplasm only and not from the cell wall, and that 

 the whole process is distinctly intraprotoplasmic. The structure of a 

 mature gland is wonderfully like that of the secretory animal cells 

 investigated by Langley,* and indeed the very words used by him in 

 the description of certain of the secretory cells will quite well 

 apply to the particular glands investigated by us, for we also find 

 that " in the mature cells the cell substance is composed of (a) a 

 framework of living substance or protoplasm connected at the peri- 

 phery with a thin continuous layer of modified protoplasm " (our ecto- 

 plasm), and that " within the meshes of the framework are enclosed 

 two chemical substances at least, viz. (&), a hyaline substance in 

 contact with the framework, and (c) spherical granules which are 

 embedded in the hyaline substance." In our case we have also to add, 

 that the whole cell is enclosed in a cell wall. We find, in other words, 

 that in the glandular cells, investigated by us, mucilage is secreted 

 in the form of drops, and that each drop is further differentiated with 

 a ground substance (gum mucilage) in which are embedded numerous 

 spherical droplets (gum). 



The mature cells which we have described are quite full of the 

 .secretion, so that the vacuole containing the cell sap has become com- 

 pletely obliterated. This is occasioned mainly by the voluminous 

 character of the secretion, which takes up water and becomes very 

 bulky. The young glands, however, display the usual structure of 

 young cells, each containing a nucleus, plastids (which in the case of 

 Osmunda form numerous starch grains), and a vacuole. Secretion 



* Langley, 1 Cambridge Phil. Soc. Proc.,' vol, 5, p. 25. 



2 D 2 



