84 
* 
point. Specimens of this Sedum and of Opuntia Missouriensis, pre- 
served just above freezing point under glass, did not shrivel; and a 
plant of Echinocactus Simpsoni^ taken under cover, after the mammae 
had been appressed by frost, expanded them to the summer condition 
in a short time afterwards. 
Assuming from these facts that the liquids in plants, which are 
known to endure frost without injury, did not congeal, it might be 
a question as to what power they owed this successful resistance. 
It was probably a vital power, for the' sap of plants, after it was 
drawn from the tree, congealed easily. In the large maple-tree 
already referred to, the juice not solidified in the tree exuded from 
the wounded portions of branches and then froze, hanging from 
the trees as icicles often six inches long. 
Photepinasty of Leaves, — W. Detmer proposes the term " pbote- 
pinasty " for the epinastic position of leaves induced by light. The 
normal unfolding of the leaves is due to paratonic nutation. The 
light first induces stronger growth in the upper side of the leaf; and 
JJ 
it is to this phenomenon that he proposes to apply the term. {^Jour- 
nal Roy. Micros. Soc.) 
Reproductive Organs of Lichens. — The most recently published 
part of Minks's Symbolss Licheno-Mycologicse treats of the Hys- 
teriace^e, Acrospermeoe and Stictidea^. On the asci and paraphyses 
together the author bestows the term " thalamium," the '^thecium 
being that portion of the apothecium which includes lliese organs. 
The structure of this portion of the lichen may be referred to three 
different types: (i) The asci and paraphyses are both fertile hyphae, 
which, in the latter case, have undergone arrest of development; 
and there are all intermediate stages between the two. (2) The para- 
physes are formed a shorter or longer time before the fertile hyphx. 
They are at a certain period indistinguishable from the hyphae of the 
fundamental tissues of the fructification, and there is here no true 
thalamium. To this class belong the true Stictide^ and the greater 
part of the Hysteriaceae. (3) Certain genera exhibit an intermediate 
structure between the first and second. 
The structure and mode of formation of the spores are described 
in detail; and it is shown that in the anthonimorphous type {Hyster- 
iiim Smilacis^ Stictis versicolor^ etc.) the mother-membrane takes 
no part in the abstriction of the spores, but that a new membrane is 
formed, the old one becoming gelatinized. 
The germination of LopJiiiim lesviusculum is described. After the 
destruction of the asci, the spores remain for a shorter or longer time 
in the fructification, where they germinate; passing over ultimately 
into a chroolepis-like gonidema, and not as would be the case if 
Schwendener's hypothesis were true, developing into a fungus- 
The two different forms of ascus correspond to the two different 
forms of spores. When the ascus has a double wall, the inner layer 
of which ultimately gelatinizes, then the spore has only a single 
membrane; while when the ascus has only a single wall the spores 
have a double membrane, the outer layer of which gelatinizes, 
{^Journal Roy. Micros. Soc.) 
