SCIENTIFIC SUMMARY. 
315 
M. Van Tieghem considers the cause which favours the formation of 
zygospores to consist in the air being impoverished of oxygen. He describes 
the germination of spores and zygospores in different media, and the structure 
and mode of dehiscence of the sporange in Pilobolus and Pilaira. 
In the systematic portion of his memoir he describes new species of Pilo- 
bolus, , Rhizopus , Helicostylum, Thcimnidium, Mortierella , and Syncephcdis , and 
characterizes a new genus, Absidia, with four species. This genus may be 
said to have the asexual growth of Rhizopus, and the sexual growth of Phy- 
comyces. From the former it differs chiefly in having the sporangiferous 
stolons of a parabolic form and cuticularized throughout, the sporangia 
alternate with the rootlets, the columella conical and slender, the membrane 
of the spores not cuticularized and coloured, and the zygospores furnished 
with a Phycomyces-like investment. If a spore is kept in a nutritive medium 
it produces a mycelium ; in a moist atmosphere, after having attained a 
certain size, it gives origin directly to a sporange without forming any 
mycelium. The zygospore behaves in a similar manner. Asexual spores, 
similar to the zygospores, are sometimes produced by a parthenogenetic pro- 
cess ; these are termed azygospores. 
The following is M. Van Tieghem’s division of the Mucorineae into 
tribes : — 
No stylospores. A 
columella in the spo- 
range, the membrane' 
of which is. . . 
Heterogeneous, i.e., formed of an "l 
upper cuticularized hood and a > Pilobolece. 
lower diffluent zone J 
Homogeneous, either all entirely 1 
persistent, or all diffluent . . . J 
Stylospores present, f Spherical and isolated Mortierellece. 
No columella in the \ Cylindrical and grouped in capi-1 s ■ A m 
sporange, which is .[ tula J ^yncepncmaea. 
— ( Journ . of Botany, May 1878.) 
Non-sexual Outgrowths on the Protlicdli of Ferns. — The discovery of the- 
non-sexual production of ferns from the prothallus originally made by Dr. 
Farlow has been confirmed by observations made upon several species. At 
the meeting of the Society of German Naturalists, held last year at Munich, 
Professor De Bary reported upon the subject as follows : — “ Investigation 
has shown that some ferns, namely, Pteris cretica, Aspidium falccctum, and 
Aspidium jilix-mas, var. cristatum, form normal antheridia on the prothalli, 
but generally no archegonia, or only imperfect ones which perish before the 
opening of the canal, and exhibit, instead of the typical formation of the 
embryo, the outgrowth described by Farlow. In those species which 
develope archegonia, no such outgrowth has been observed. The morpho- 
logical phenomena presented by the shoot are alike in the species named, 
even in the smallest particulars. In the prothallus, which grows directly 
out of the spore, the development which occurs in most cases, and may be 
called normal, is as follows : — At the sinus, nearly at the spot where the- 
first archegonium occurs, there arises a protuberance which grows out 
directly into a leaf ; at the base of this, close by the insertion into the pro- 
thallus, there is formed an aerial punctual vegetationis, on which a second and 
the successive later leaves appear. At the base of the first leaf there is 
formed, endogenously on the vascular bundle, the first root. As soon as 
the second leaf appears the bud grows like an ordinary fern-shoot. Varia- 
