DR. NYLANDER ON GONIDIA AND THEIR DIFFERENT FORMS. 43 
action in Lichens is especially superficial, it thence results that the 
stratum of the gonidia increases but little in thickness, though it is 
extended along with the extension of the thallus, and there occurs 
at the same time a twofold method by which the gonidia are 
multiplied — the one intracellular and the other by the addition of 
a protococcoid division, the former, however, being the more 
prevalent. 
I have made mention of the origin of gonimia in Bullet. Soc. 
Bot. Fr., 1873, p 264, Cfr. Nyl. in “ Flora,” 1868, p. 353. 
It is evident that the notion of gonidia assumes at the present 
day a wider sense than that in which it was formerly regarded. 
The question, however, concerning zoospores developed in common 
gonidia remains very doubtful. Such I have not seen in gonidia 
subjected to experiment,* nor have I ever found in the gonidia of 
the thallus. It is plain, moreover, that zoospores, even if nature 
allowed them to be formed in gonidia, closely surrounded by the 
elements of the thallus, could not there have egress from the 
gonidia, and would have no space in which to move. Nature thus 
does not err, never commits sucli illogisms, and the formation of 
zoospores would truly be sheer stupidity, since their physiological 
action would thus be in vain without any possible effect. How- 
ever, it is not to be denied that zoospores may be generated in free 
gonidia (that is, not stratified in the thallus) ; at least, there the 
thing is possible, and in no way absolutely contrary to the constitu- 
tion of Lichens. And this, indeed, seems to be persuaded by 
Chroolepus,^ which readily embraces Lichens, thougli most fre- 
quently in a sterile condition, just as, besides these, examples of 
types from other quarters, especially amongst the Liclienacei, are 
not wanting, which never fructify. Fertile chroolepa may be seen 
in the “ Flora,” 1873, p. 22, and 1875, p. 106. 
Here, perhaps, in passing, it may be convenient to repudiate in a 
few \vords the Schwendenerian hypothesis, against which I have in 
several places, and in the “ Flora,” 1870, p. 52, brought forward 
certain observations, and especially have recorded that gonidia 
“ algm ” (according to that hypothesis) would constitute singular 
and unhappy dwellers in darkness,;]; inclosed in thalli, detained in a 
* There originate then, indeed, very readily, zoosporoid Infusoria (which 
I have seen multiply by a longitudinal fissiparity, as it is called), but I 
could never observe zoospores formed in the gonidic cellules themselves. 
t Chroolepus, from to Xstto^ Xen-eor, and therefore neuter. The articula- 
tions which produce the zoospores in Chroolepa may be called by a very 
natural and very simple term zoogonidia. This name in A-lgology has 
been very perversely employed for zoospores, which may be compared with 
the contents of the gonidia, and not with the gonidia themselves. Equally 
improperly the zoospore-producing articulations of Chroolepa (our zoogo- 
nidia) have in Algology been termed “ sporangia/’ a name elsewhere 
already bearing a different conception. 
X Th. Fries, coming to the aid of his ” friend ” Schwendener, in Lich. 
Scand., p. 4, affirms that this is “ not true.” But if this w'ere not true, all 
thalli in a moist state would become green, which “ is not true,” for only a 
very few thalli in the time of rain are truly green {e.g., Physcia ciliaris, 
