THALLOGENS. . 225 
enclosed in special receptacles named sporanges, in other cases they 
are quite destitute of any envelope. In short, the reproduction of 
thallogens is often the result of organic dispositions, quite special, 
which admit of no general description, and which can only be 
made intelligible by describing each individual case. 
To examine all the families which constitute the class would be 
an immense undertaking. We shall confine ourselves to examine 
attentively certain types of the five families by Alge, Fungales, 
Lichens, Mosses, and Ferns :— 
Sus-Crass, CLAss I.—THALLOGENS. NATURAL ORDERS. 
I. Diatomacez, or bush nuts. 
Cellular flowerless plants, nourished by the Il. Conifers 
1, ALGALES, 4 medium on which they vegetate; propagated{ III. Fucacese, or sea-weed. 
by zoospores, spores, or tetraspores. . Ceramiacee. 
by 
etime destitute of green 
. Boi : 
X. Ascomycetes, or morels. 
gonoids. 
XI. Physymycetes, or moulds, 
g 
2.F {age thallus, living on air, propagated by spores, | VIII. Goniomycetes, or blights. 
UNGALES. Ee ee ee if pat ps IX. Botrytacee, or mildews. 
Cellular flowerless plants, nourished through ; : 
Ln their whole eurface by the medium on which | XII Graphidacez, cell-lichens. 
CHENALES.4 they vegetate, living on the air propagated by< XIII. Collemacez, or jelly-lichens. 
he seer enclosed generally in asci, with green ead Parmelliacez,or leaf-lichens. 
gonoidea in their thallus, 
VI. Agaricacez, toad-stools. 
Cellular flowerless plants, nourished through | VII. Gasteromycetas,or puff-balls. 
y { 
I. DIaToMacEz. 
: Crystalline fragmentary bodies, which attach themselves to 
_ Stones constantly under water, and so obscure in their organisa- 
tion that it still remains a grave question whether they belong more 
to the animal or vegetable creation. Ehrenberg inclines decidedly 
to the former opinion, assigning as ,reasons that they exhibit a 
peculiar spontaneous movement, produced by locomotive organs ; 
that many of them have a lateral opening, round which are 
corpuscles, which become blue when placed in water coloured with 
indigo, like many Infusoria ; their shells, or shield, are in structure 
Similar to the Molusca. Schleiden considers that such an artificial 
‘nd complex structure as exists in the Diatomacea is without 
explanation ; of great significance, and without “analogy in the 
___-Yegetable world.” 
“ On. the other hand, the discovery of Mr. Thwaites discloses 
| oem strictly in accordance with what occurs in the animal 
a om. In Fragilaria pectinalis, two individuals closely approxi- 
ted dehisce in the middle of their long diameter ; four pro- 
Q 
