1%] ORIENTATION OF THE PLANT EGG 303 
stants. Alone among Bryophyta the embryo of Riccia 
including here also the closely allied genera Ricciocarpus 
ad Ricciella) shows very slight distal-proximal specializa- 
tion, if any. The archegone stands perpendicularly upon the 
thallus, invaginated for protection, and the originally distal 
temisphere develops in essentially the same manner as the prox- 
imal. The mature sporophyte, a globular body less than a mil- 
limeter in diameter, consists merely of a one-layered wall of 
sterile cells surrounding a homogeneous mass of spores, elaters 
being absent. The spores are released by disruption of the wall 
and disorganization of the surrounding tissues of the invaginated 
thallus and the calyptra. 
Embryogeny of Spherocarpus.— This interesting little plant was 
Mt carefully investigated until 1867, when Petounnikow made 
*ut some of the principal points in the embryogeny‘ after the 
‘arly stages which apparently he did not see. In 1875 Kienitz- 
Gcrloffs took in hand the investigation of this plant and practi- 
a completed it. He showed that while a considerable irreg- 
tarity existed in young stages, the first wall was approximately 
Metre. This was succeeded by one or two other transverse 
dn rencipally in the hypobasal hemisphere, and finally peri- 
“and anticlines in the epibasal hemisphere served to delimit 
“eamphithecium and endothecium of the capsule. Leitgeb® 
ON @ series of figures of the young embryo which together 
i. the excellent series of Kienitz-Gerloff in the paper cited 
ag regarded as complete. Leitgeb suggests that its embry- 
: 8a “strongly resembles that of Fossombronia,”’ but its resem- 
the seein Strongest with the Marchantiacee, and probably 
ae the plant is not with the Jungermanniacee as asia 
dana Ty have thought, but with the simpler relatives of ee 
oe ; he mature sporophyte is a spherical capsule provide 
' aay aes ees du Spherocarpus terrestris Mich. Bull. Soc. Bot. 
. 1867, 
143137. 1 
eas 
Neue Beitr, zur E 
a * i + Zeit. 
é 795, 1875, ntwickelungsgesch. des Lebermoos-Sporogoniums. Bot 
6 > 
Op. cit, 4:69. p/. 9. 18709, 
