from the Cell-contents of the Characeae. 3 



in the species of Nitella on which I have been making observa- 

 tions, is l-4300th of an inch in diameter. Iodine with and with- 

 out sulphuric acid gives it a dark brown-red colour, but does 

 not turn it or its contents blue. 



Mucus-layer. — Immediately within the green layer is a gra- 

 nular, colourless mucus, which is unequally and unevenly spread 

 over the surface, so that it presents a wavy line towards the axial 

 fluid. The unevenness of the inner surface of this mucus arises 

 from partial aggregations of its substance, which are most pro- 

 minent and accumulated midway between the lines of repose. 

 One of these aggregations is generally larger than the rest, and 

 this in the spiniform cells which terminate the branchlets and 

 in the early state of the internode itself contains the cytoblast, 

 which with its acconipanying mucus also at this early period 

 lines the inside of the cell ; so that the whole of the granular 

 mucus-layer and its contents, which afterwards form such a large 

 portion of the internode, is developed from this cytoblast, and 

 should be regarded as merely an increase in quantity of the ori- 

 ginal protoplasm or primordial utricle of Mohl. 



We have now to direct our attention to the contents of the 

 granular mucus, which, when one extremity of the internode is 

 truncated by a sharp cutting instrument, under water, rushes 

 out partly in a loose amorphous form, and partly enclosed in 

 vesicles of variable dimensions, the largest of which are some- 

 times nearly as wide as the internode. Both the amorphous 

 masses and vesicles are again charged with vesicles of different 

 sizes, circular disks containing a tinely granulated substance, 

 subreniform or round starch-globules, and a number of irre- 

 gularly-shaped bodies of different sizes, but of which none exceed 

 the 1500th part of an inch in diameter. 



The most striking of these contents are the circular disks, 

 which, from their defined outline and uniform size and appear- 

 ance, are easily distinguished from any of the other bodies. 

 They average about the 2150th part of an inch in diameter, and 

 appear to be filled with a minutely granular mucus of a very 

 faint yellow colour, which, a certain time after the disk has been 

 exposed to the water, contracts into an elliptical form, and thus 

 shows that it is enclosed within a capsule, from which it is also 

 distinct. These disks may be seen in considerable numbers 

 loose or imbedded in the amorphous masses of mucus, or in 

 that filling the large vesicles, or in variable plurality in trans- 

 parent globular vesicles otherwise empty ; lastly, they may be 

 seen fixed singly to, or in the wall of a vesicle, which appears to 

 be their normal appendage, and though this vesicle is sometimes 

 hardly distinguishable, it is at others five or six times the dia- 

 meter of the disk. Iodine colours the nucleus of a deep brown 



1* 



