356 Goebel. — On the Simplest Form of Moss . 
constitute the main portion of the Liverwort, but is merely the 
portion which bears the sexual organs to which the leaves 
serve as involucres. These forms seemed to me to represent 
a primitive type. 
If, now, we suppose a case in which the formation of the 
sexual organs is deferred to a later stage of development, 
whilst the leaves function as assimilatory organs, the result in 
such a case would be to shorten the protonemal stage of the 
life-history, a state of things which is actually realised in the 
Mosses. The simplest form of Moss would then be one in 
which the sexual organs are directly borne, with or without 
an involucre, on a filamentous protonema. 
It would seem to be scarcely probable that such a form 
is still to be found among existing Mosses ; but, as a matter 
of fact, it does exist under the name of Buxbaumia. This 
Moss is usually included among the higher Bryineae, but 
erroneously, for the sexual generation is so wonderfully simple 
that it very nearly comes up to the hypothetical ideal of the 
simplest primitive Moss. 
The protonema of Buxbaumia resembles that of the other 
Mosses ; it is peculiar only in that the filamentous branches 
frequently anastomose. 
The male plant has no stem : it consists of a branch of the 
protonema bearing a single terminal antheridium. The 
antheridium differs in its form from that of Bryineae, and 
resembles that of Sphagnum and of many Liverworts in that 
it is globular and is borne on a long stalk ; it is invested by 
a leaf forming a conchiform involucre. The leaf, which is 
destitute of chlorophyll, differs in the arrangement of its cells 
from the leaves of the Bryineae in that it has at its apex, not 
a two-sided apical cell, but cells arranged in slightly diverging 
anticlinal series. The habit of the male plant is, in fact, such 
that, were it found occurring alone, it would be classed as an 
Alga without much hesitation. 
The female plant is somewhat more highly developed. On 
a mass of tissue, which represents a rudimentary stem, is 
borne an archegonium surrounded by several involucres which 
