LEPTOGIUM. ] COLLEMEL. : 67 
8. L. cretaceum Nyl. Act. Linn. Soc. Bord. sér. 3, i. (1857) 
p. 270; Syn. i. p. 120.—Thallus rosulato-lobulate or stellato-laci- 
niate, olive-brown or dark-olive; the lobes unequal, crenate, almost 
imbricate. Apothecia small, nearly biatorine, concave or gyalecti- 
form, pale reddish-brown, the margin entire, paler; spores ovoid, 
3-7-septate, with longitudinal septa, 0,022-40 mm. long, 0,011- 
17 mm. thick.—Mudd, Man. p. 45; Cromb. Lich. Brit. p. 7; Leight. 
Lich. Fl. p. 32, ed. 3, p. 27.—Enchylium cretacewm Gray, Nat. Arr. 
i. p. 398. , Collema cretaceum Sm. Eng. Fl. v. p. 210. Lichen 
eretaceus Eng. Bot. (1800) t. 738. 
This plant appears at first as minute, very thin, olive or dark stedle, 
somewhat immersed and ‘distinct. These become more prominent, ap- 
proximate and confluent, till it attains the perfect state. It is occasionally 
seen in an isidiomorphous condition. The gonimia are rarely moniliform. 
The apothecia, seen only in the best developed specimens, are small in 
the scattered, and moderate in the confluent rosue. 
Hab. On cretaceous and siliceous nodules in moist shady places in 
upland tracts— Distr. Confined to the Chalk and Oolite districts of 8. 
and W. England ; probably in its young state often overlooked.—B. M.: 
Near Folkestone, Kent; Plumpton and West Dean, Sussex; Reigate 
Hill, Surrey ; Isle of Wight ; Brighton Downs, Sussex ; near Northleach, 
Gloucestershire; Stokesay, Shropshire. 
9. L. microscopicum Nyl. Bull. Soc. 
Bot. Fr. iv. (1857) p. 920; Syn. i. 
p. 122, t. 4. f. 17.—Thallus effuse, very 
minute, fruticulose, erect, branched, 
olive-brown, dark-brown or blackish ; 
branches slender, elongato-papillate, un- 
equally rounded, somewhat constricted a 
or attenuate at the base. Apothecia 
very minute, scattered, concave, pale 
brown or brownish-red, the margin 
smooth, entire ; spores .ovoid or oblong, 
3-5-septate, and murali-locular, 0,022- 
27 mm. long, 0,009-14 mm. thick.— 
Cromb. Journ. Bot. 1874, p. 336; 
Leight. Lich. Fl. Suppl. p. 468, ed. 3, 
p. 34.—Brit. Hxs.: Cromb. n. 7. 
In its earlier stages of growth this has 
the appearance of a Strosophon. The thal- 
lis is cellular, and the gonimia are often 
3-moniliform. Though resembling a mi- 
nute state of L. lopheum, it is distin- 
ished by its peculiar habit and the - Fig. 17. 
orm of the spores. It is very rarely Leptoyium microscopicum Nyl. 
fertile. On the thallus is occasionally —«. Thallus, x30. 0. Sec- 
seen a parasitic Obryzum described here- tion of apothecium, x30. 
after. c. Three spores, x 500. 
Hab. On slaty rocks, but chiefly on chalk pebbles and calcareous walls, 
F2 
