Marcu 4, 1897 | 
mA TORE 
423 
But side by side with this sexual generation, there is evidence 
of two other modes of propagation amongst the Characeze. 
(i.) It is believed by some botanists to be established beyond 
doubt that in the case of Chara crinita in the regions of the 
Baltic Sea, if not elsewhere, the unfertilised archegones produce 
plants like fertilised ones. 
(ii.)sSome species of Chara are propagated by bulbils or 
agglomerations of cells, by branches known as gymnopodal 
shoots, or by prothalloid branches. 
We are thus in the presence of facts of the last importance on 
the theory of reproduction. We find an organism with organs 
specially adapted to and formed for reproduction, and yet the 
same result is brought about by other parts of the plant, which 
seem to have no such special organisation. 
And, secondly, we find that the result.of these short cuts to 
reproduction excludes or avoids the sexual act. 
Muscinee.—Here the full life-history may be represented as 
follows :— 
ae 
Protonema 
Oophore ... Bla 
Cormophyte, f Archegone 
producing \ Antherizoid 
el 
f Sporogone (seta and sporangium) 
Sporophore- | 
Spore 
But side by side with this somewhat elaborate life-history, the 
mosses exhibit abbreviated modes of reproduction of varied 
descriptions—a multiplicity of methods of what I will venture to 
call, by borrowing a term from a popular branch of applied 
science, short-circuiting. 
First we get the production 0. gemmz which produce proto- 
nema like that arising from the spore, and this protonema, 
through the intervention of a bud, produces the cormophyte. 
These gemme are found ina great variety of positions : in the 
capsules in Encamptodon (Wezss¢a perichetzalts), in the place of 
spores (Montagne, ‘‘ Plantes Exotiques Nouvelles,” Azz. de Sc. 
Wat, Rot., vol. iv. pp. 119, 366): in the terminal cups which 
probably represent male flowers in the well-known Zetraphis 
pellucida ; congregated in balls at the ends of quasi pedicels in 
Aulacomnium palustre; on the ends of the leaves in the 
Orthotrichum phyllanthum (where the fructification is very 
rare); in Leptodontium gemmasceus and Grimmia hartmanni ; 
on the upper half of the midrib in Zortila papillosa. 
The next step in the abridgement of the life circle is ex- 
hibited by those cases in which protonema is produced by the 
cormophyte without the intervention of a gemma. ‘* Pringsheim | 
and Stahl found independently of one another,” says Prof. Bower 
(wbisup.), “that itis possible by cultivation under abnormal 
circumstances to induce a formation of protonema by direct vege- 
tative growth from the sporogonium of certain mosses.” But 
nature herself, apparently under no abnormal circumstances, 
brings about the same phenomenon. Schimper has traced the 
growth of protonema directly from the rhizoidsin Phascur ser- 
vatun. (** Recherches sur les Mousses,” p. 11), and Polytrichum 
nanunm and aloides (p. 12); from the stems in Décranwm 
undulatum (p. 13); from the under side of the leaf in Ortho- 
trichum obtustfolium (P1. ii. fig. 6) ; from the mid-rib of the leaf 
in Orthotrichum Lyellé (p. 15); from the perichztal leaves in 
Oncophorus glaucus (p. 18); from the base of the leaf in 
Funaria hygrometrica(p. 19). It has been found growing from 
the marginal cells of the involucres of the archegone in the 
strange Buxbauméa aphylla (Goebel, on ‘The Simplest Form 
of Moss,”’ Avn. Bot., vol. vi. p. 355). Lastly, in Conometriumn 
julianum young plants often grow from the inner side of the 
calyptra with the intervention of a short piece of protonema 
(Goebel, ‘*Outlines of Classification,” Eng. Tr., p. 173). 
But nature goes yet another step forward, and leaves out in 
some cases at once gemma and protonema; and the cormo- 
phyte produces bulbils which at once again grow into cormo- 
phytes. Thus on the rhizoids of Garbula muralis, Grimmia 
pulvinata and trichophylla, and Trichostomum rigidulum are 
formed leaf-buds, which develop into the true cormophyte 
(Schimper, 10-11): bulbils grow on the stem of Aryum 
annotinun (p. 14) ; and, lastly, we get the striking phenomenon 
of young cormophytes produced at the ends of the branches in 
NO. 1427, VOL. 55] 
Sphagnum cuspidatum, resembling in everything but in size the 
parent plant from which they are produced (Schimper, ‘‘ Tor- 
fossoose,” pl. 16, fig. 1). This is very striking: here nature 
has given the slip to spore, to gemma, to protonema, to leaf-bud 
short-circuiting can go no further. 
The first inquiry I suggest on the foregoing statement of 
facts is this: Taking the life-history of a moss in its fullest form, 
is it correct to say that there are two generations involved in 
it? And this will turn upon what we mean by a generation. 
_ Generation.—If we regard the alternation of generations as 
it exists in the Medusee and hydroid zoophytes, to which the 
expression, now so familiar, was, I believe, first applied by 
Steenstrup, it will be found that in these creatures, each 
generation consists of a distinct and independent organism, 
differing from the case of generations of men in that the one 
generation is produced asexually by germination, and the other 
sexually, and that the organisms of the two generations are 
different in form. The generative zooid or Medusa is detached 
from its stationary parent: and in like manner the young 
creature produced by the Medusa is detached from it before it 
begins to develop into the fixed hydroid colony; in the 
case of each new generation there is a complete solution of 
continuity with its parent; there is no physical connection 
maintained after a certain period, and there is no dependence 
for nutrition or any other vital process. But when we turn 
to the moss we find no such division into independent organisms 
between the oophore and the sporophore, but, on the contrary, a 
continued physical connection, and dependence of the seta and 
sporogone on the cormophyte. The two parts are organically 
connected. The seta and sporange are incapable of an in- 
dependent existence, and are not detached from the moss plant 
except by death. 
I suppose that a generation might, according to the ordinary 
understanding, be defined to be the life of an organism either 
independent in fact or constituted for an independent existence 
from the time when its whole future was gathered up into 
one cell to its death: but is not usually extended to include 
the life of a part of an organism from the time when the future 
of that part was gathered together into a single cell. : 
How are we to distinguish a new generation from the growth 
of a part in an existing structure? I suppose that a new 
generation means the origination of a new individual ; that so 
long as there is a physical continuity in a given structure, 
both in fact and in design, we have the same individual ; that 
so long as this exists, the death of a part of the structure does 
not convert the remaining part, or the parts which may arise 
from it, into a new individual; and that, in short, we never 
have a new generation without the solution of continuity, in 
fact or in design, between the old and the new. If we adopt 
the view above suggested of a generation, there is not in the 
life-history of the moss more than a single generation, and there 
is consequently no alternation of generations. 
To extend the definition of a generation so as to include the 
separate development of dependent parts, would, no doubt, 
remind us of the fact that in the earliest stages of organisation. 
growth and reproduction seem hardly to be distinguished ; but 
it seems to me to confound together two things which it is most 
important to separate when we are considering the course and 
history of reproduction. ; 
In this connection it is convenient to consider the meaning of 
the words ovwm or ovule. By these words I conceive that 
botanists mean a cell resulting from the union of two other cells 
of different characters, from which cell a new generation starts. 
The ‘‘ embryo which begins the new generation is the female or 
germ cell (ovum, oosphere, germinal vesicle), says Sachs. 
That it shall be the beginning of a new generation—of a new 
being, either independent or constituted for independence, is, ii 
conceive, an essential part of the meaning of the word in ques- 
tion. If so, there is in mosses no ovum and no oophore ; 
for the fertilised archegone produced in mosses 1s not an inde- 
pendent organism, but a dependent organism or part of an 
organism ; and the really startling fact about this history of the 
moss appears to me to be this: that whereas in the generality of 
cases the fertilised ovum is itself and directly the starting-point 
of a new individual, in the moss the fertilised ovum produces a 
new growth, and that this new growth by subdivision produces 
a number of spores, each of which is the starting-point of anew 
individual. But this process in the mosses does not stand alone. 
It recalls the mode of reproduction in other cases. In some of 
the Florideze the fertilised ovum does not directly reproduce a new 
