Features contrasting and comparing Lithothamnion corallioides, L. glaciale and Phymatolithon calcareum

(Derived from Irvine & Chamberlain, 1994)


L. corallioides

L. glaciale

P. calcareum

Colour tendency (fresh) Brownish pink Reddish to deep pink with violet tinge Mauvish brown
Thallus surface Covered with low mounds Mainly smooth, some scattered low mounds Some lowish mounds, frequently flaky areas
Thallus texture Slightly glossy Matt Somewhat chalky
Branch hardness Brittle Hard Quite hard
Branch size Mainly < 1 mm diameter Variable Mainly >1 mm diameter
Crustose plants in vertical section
Epithallial cells Mainly flared Mainly flared Mainly domed
Cortical cells

l x d


5-35 x 5-10 mm


8-12 x 4-8 mm


5-10 x 3.5 mm

Cortical fusions Very extensive More localised More localised
Groups of fused cells Star-like Bead-like Bead-like
Primary pits Occupying entire end wall  

Occupying only centre of end wall

Occupying only centre of end wall
Medullary filaments 5-6-layers To 17 layers 5-6 layers
Medullary cells (length

x diameter)

10-30 x 5-12 Fm 7-26 x 3-8 Fm  

8-18 x 7-10 Fm

Branch anatomy in longitudinal section
Medullary cell distribution Tiered Tiered Not tiered
Medullary cells Ixd Rectangular

20-35 x 8-12 mm

Elliptical to rectangular

3-18 x 3-11 mm


5-18 x 3-10 mm

Medullary cells pits Bilenticular primary pits Not known Not bilenticular primary pits
Cortical cells lxd 5-35 x 5-10 mm 8-12 x 4-8 mm 8-18 x 7-10 mm
Tetrasporangial/bisporangial conceptacles
Shape Without rim; pore plate convex With narrow, non-raised rim; pore plate level Either with rim and prominent, or without rim and immersed; pore plate level
External diameter To c. 350 mm To c. 380mm To c. 450mm
Pores SEM Ringed by 5 cells SEM Ringed by 6 cells SEM Ringed by 6 cells SEM
Chamber VS diam. 234-380 mm 150-360 mm 230-350 mm
height 83-117 mm 110-180mm 117-130 mm
Roof thickness 29-39 mm 5-40 mm 30-40 mm
Shape Long and thin Elliptical Plump
Length 78-86 mm 65-96 mm 90-125 mm
Diameter 21-26 mm 23-47mm 49-73 mm
Old conceptacles Not known Usually becoming buried Becoming buried