semi-cells also octogonal with slightly convex sides and apex
each semi-cells with 2 pairs of spines and 2 single spines
length 45–55 µm (without spines)
in center of semi-cells a wart surround by a ring of small warts
on both sides of the isthmus a papilla
one parietal chloroplast with two pyrenoids per semi-cell
So far I have only found Xanthidium cristatum var. papilliferum in the Simmelried and in the Paradieswiesen. However, it has not been found in the Simmelried since 1995 any more.
Xanthidium cristatum var. papilliferum stands out even at small magnifications due to its long spines and symmetrical shape. However, many subspecies have been described within the species Xanthidium cristatum. To determine the subspecies, the cells must be examined closely at high magnification. In the case of Xanthidium cristatum var. papilliferum, small papillae located to the left and right of the isthmus are important for identification (s. figs. 1 b and 2 b). There are therefore two papillae per semi-cell.
The cells from the population from the Paradieswiesen were about 70 µm long (without spines), about 25 % larger than indicated by Lenzenweger (1997). However, since all other characteristics correspond to the description of Xanthidium cristatum var. papilliferum, this is obviously within the usual variability of this species.
Fig. 1 a-b:Xanthidium cristatum var. papilliferum. L = 72 µm (without spines). Two focal planes of a slightly squashed specimen. Note the papilla (PA) in the sinus between the semi-cells. Obj. 100 X.
Fig. 2 a-b:Xanthidium cristatum var. papilliferum. L = 72 µm (without spines). The same specimen as shown in fig. 1 a-b in brightfield illumination. PA = papillae on both sides of the isthmus. Obj. 100 X.