290 PROCEEDINGS OF SECTION D. 



in var. Deipontei (the stouter Ehrenbergii) there are six ; and in 

 forms of traheciila itself eight or ten. In CI. rostratum also, and its 

 var. Ktdzingii, the chloroplast is generally simple, or at any rate 

 the ridges are not very marked. I have observed, however, 

 a mixed form of these two, showing plainly six well-defined 

 ridges. In Cosmariiim the chloroplasts divide vertically, prior 

 to the division of the pyrenoid into two. 



Membrane. — Too much weight must not be placed upon the 

 character of the membrane as an indication of specific distinctness 

 or specific identity. All the cell-membranes are smooth and 

 colourless to start with. CI. decorum var. Deipontei, for example, 

 is strongly rufescent and decidedly striate, but I have observed 

 well-grown forms almost colourless but still striate, and young 

 forms rufescent, but without striae. In gathering 53 N.H.S. also 

 I noted a fine specimen of this species 516// long, perfectly colour- 

 less except towards the tips, which were slightly yellow, nor could 

 a trace of striae be detected upon the membrane. In slide 10 

 N.H.S. there may be seen specimens of CI. tiirgidum also, quite- 

 colourless and with striae hardly visible, accompanied by its var. 

 Pritchardianum in the same condition and much resembling CI. 

 acerosum. 



Again, the fineness or coarseness of the striolation is no 

 criterion. Some species do indeed show finer striae than others as 

 a regular thing, but it does not follow that a form with costae is 

 therefore no connection. I have observed CI. ttirgidum with one 

 semi- cell costate, the other normal ; also its var. Pritchardianum 

 with a costate portion at each end, the central gi'owth being, 

 striolate. The costje of such cells is hardly an irregularity, it is 

 a definite alternative method of growth ; the normal striolation 

 forms later, as I have myself noted, by one or more striae developing 

 between the costcB, the general striolation becoming regular. 



Further, the punctulation or scrobiculation of the membrane 

 proves nothing. Doc. trabecula, for instance, has been found with 

 a faintly-scrobiculate, puncta-scrobiculate, strongly-scrobiculate, 

 granulate, and even incrassate-reticulate membrane {Jour. Linn. 

 Soc. N.S.W., 1910, PI. ii, f. 21). I have observed also a cell with a 

 strongly-scrobiculate patch on one side, the remainder being only 

 faintly-scrobiculate. Truncatum and Ehrenbergii may be found 

 with all these different membranes (cf. PI. i, f. 3), the latter even 

 spinous with incrassation {PL Hntchinsonii (Turn.), W. & G. S. 

 West, Monog. PI. 31, f. 7). Almost all Cosmaria are at least punc- 

 tate when closely examined, and the punctulation or scrobiculation 

 generally becomes more obvious in their more fully- developed 

 forms or older condition. This accentuation is merely the result of 

 incrassation. In very degenerate forms again puncta spots or 

 scrobiculae often take the place of the puncta-granules that after- 

 wards appear. Lately I noticed a cell of Cos. biretum perfectly 

 smooth outwardly (shde 3b also), the granules being replaced by 

 scrobiculations within. Also an unequal cell of Cos. magnificuni. 

 was observed, one semi-cell normal, but in the other and growing. 



