IN VEGETABLE BIOLOGY. 005 



being by no means improved upon by Hick *. Its rarer congener, 

 C. mamillosus, shows continuity in a still more striking form. 

 The tballus of both may be said to be formed of two orders of 

 cell — outer small elliptical ones placed in longitudinal rows per- 

 pendicular to the surface, and inner larger ones provided with 

 radiating arms, aptly compared by Mr. Hick with multipolar 

 nerve-cells. Both authors figure continuity throughout the 

 thallus, in the outer cells by means of fine threads, on which the 

 rows appear like strung beads, in the inner ones by the coalescence 

 of their arms, " uniting to form a network," as Zanardini says of 

 his C. ? adriaticus. The arms of the inner cells of C. mamillosus 

 are much longer than those of G. crispus, and the lumen is some- 

 times reduced to a mere junction -point of the arms (fig. 20). In 

 many cases the arms of neighbouring cells are not continuous, 

 and the cells are placed in communication by means of a single 

 fine thread of protoplasm, at or near the centre of which is placed 

 a shining bead-like nodule, through which the thread passes 

 without undergoing division. In other cases a nodule is not seen, 

 and the arms of neighbour cells appear to simply coalesce. The 

 small outer cells are more numerous than is the case with 

 G. crispus ; they unite with their under- and overlying as also 

 with their lateral fellows by single fine filaments, which may or 

 may not be provided with a nodule. In no instance was it found 

 possible, with sections well stained with Judson's Oxford blue, to 

 resolve the connecting filament into two or more, nor was any 

 evidence obtained of its division in passing the nodule. 



Polyides eotundatus. — A section of the thallus in a plane at 

 right angles to the axis of growth shows that it may roughly be 

 said to consist of three tissue-areas: — 1st, the epi- and hypodermis, 

 composed of small cells more or less elongated perpendicularly to 

 the surface ; 2nd, a middle zone of larger cells filled with starch- 

 granules ; 3rd, fibre-like cells forming the central mass. A view 

 of this is given at fig. 22. Continuity seems to hold throughout 

 the thallus of this type, although it is impossible to see the con- 

 nections of all the cells in any one section. Also, the continuity 

 is direct, by means of a slender thread upon which a small nodule 

 staining well may frequently be seen. By means of these threads 

 the epidermal cells unite, either singly or in pairs, with a cell of 

 the subjacent layer, which itself communicates, alone or with its 

 lateral fellow, with the longer cell immediately beneath it ; and 

 * L. c. tab. 244. fig. 12. 

 LINN. JOUBN. — BOTANY, VOL. XXI. - Y 



