54 
NEW ARRANGEMENT OF 
examination of many specimens we have also ascertained 
that the calyptra is actually mitriform ; though^ from its ir- 
regular splitting at the base, it sometimes appears with one 
predominant fissure, or dimidiate, as in Hedwig's figure : 
this plant is therefore a true Orthotrichum *. 
PLATE II. 
Fig. 1. Theca of Gymnostomum Donianum, shewing the 
elongated columella. 
2. A young plant of the same species. 
3. A mature calyptra of the same. 
4. Theca of Gym. microstomum, with the membrane 
within the orifice. 
5. Theca of Gym. Griffltliiamim exhibiting the same 
structure. 
6. Theca of Gym. viridissimum. 
7. Theca of Gym. involutum divided, to shew the 
columella. 
8. Calyptra of the same. 
9. Theca of Gym. 'pyrtforme, with the expanded 
membrane within the mouth. 
10. The mouth of the theca of the same dissected, 
and more highly magnified ; it exhibits the sum- 
mit of the columella expanding into a membrane 
which is attached to the top of the lining of the 
theca ; the sporules are seen within. 
11. Calyptra of the same species when full grown. In 
a young state it is almost mitriform. 
* We find that Bridel once formed a genus of this plant, called Anodoji' 
tium, which Mr Brown seems rather inclined to favour, by menlioning, in 
Linn. Trans,, vol. x. p. Slo., that he had ascertained two new species. 
Bridel, however, in hjs Methodus nova Muscorum, reduces the genus again 
to Gymnostomum. 
