110 Mr. H. J. Carter on the Development of Gonidia 



Probably the best way of pursuing this part of the subject is 

 to commence with the development of the new plant from the 

 nucule, by which we shall see under what form the mucus first 

 appears. 



The nucule of Char a verticillata (fig. 35 a), which is more or 

 less ovate, consists of three coats, viz. an external or cellular, a 

 middle or laminar, and an internal or delicate one, within which 

 is enclosed a quantity of starch and oil, together with a little 

 mucus. 



The external coat [h, b) is composed of five long cells, twisted 

 twice round the middle coat, side by side, so as to form a 

 spiral plane, ending at the apex in a group of ten cells, the last 

 of which are pointed ; this group has been called the coronet. 

 They all, and in every respect, answer in structure, &c. to the 

 description given of the internode of Nitella in my first paper. 



The middle coat {e, e), which represents in relief and depres- 

 sion the spiral lines impressed upon it by the cellular one, 

 consists of several very thin laminae, structureless, homogeneous 

 in composition, and of a dark brown colour by transmitted, but 

 black by reflected light. 



The internal coat {d, d) is a fine delicate colourless membrane, 

 which frequently adheres very strongly to the middle coat, and 

 so much resembles the laminse in the latter, that the whole 

 together present a structure similar to that of the thickened 

 cells in old filaments of Conferva glomerata. When treated 

 with iodine alone, this, as well as the middle coat, assumes a 

 reddish-brown colour ; but when sulphuric acid is added, the 

 internal coat (as well as the next layer to it, which ought per- 

 haps to be considered a part of it) turns blue, while the middle 

 coat remains unaltered. 



The starch and oil are in pellicled smooth grains, of a sub- 

 round, subangular, elliptical or compressed form. These grains 

 are larger in the centre than at the circumference, where they 

 become almost molecular, and are mixed up with a layer of 

 mucus, which supports the whole in an ovoid form. 



This external mucus may be the preserved protoplasm, and 

 there may be a cytoblast also ready to assist in the formation of 

 the first cell ; as in Spii^ogyra, where both protoplasm and cyto- 

 blast appear immediately the contents of the resting-spore burst 

 forth to form the new cell. 



Such is the composition of the nucule, in the contents of 

 which I have never seen anything like the " globular vesicles " 

 of the mucus-layer; not even where the germinating matter 

 has perished, and the nucule has remained for several weeks 

 afterwards exposed to the decomposing action of the water. 

 Neither have I even seen anything like the globular vesicle, or 



