114 
PROGRESS OF MICROSCOPICAL SCIENCE. 
and occasionally a fair quantity of picotite, with, of course, oxides of 
iron. Hence he concluded that, as had been already shown as 
regards some other serpentines, that of the Lizard was the result of 
the hydrous alteration of an olivine rock, such as lherzolite. 
Microscopical Structure of Rocks. — Professor Zirkel, one of the 
first authorities on the microscopic structure of rocks, has written a 
part of vol. vi. of the Keports of the United States Geological Ex- 
ploration, of which an important and long notice appears in 
‘ Silliman’s American Journal’ (April). The report commences with 
an introduction reviewing the kinds of crystalline rocks and their 
microscopic distinctions. In this chapter Professor Zirkel states that 
in his descriptions he uses the term “ ground-mass ” for the mass of a 
rock where it is distinctly crystalline granular under the microscope, 
and “ base ” when there is an amorphous paste not crystalline granular 
under the highest magnifying power, though containing, except in 
many obsidians, crystalline minerals. He remarks also on the 
evidence that the crystalline minerals in the “ base ” were formed 
while the latter still had a flowing movement, as shown by the 
minerals ranging in straight or wavy lines, and by their fractures 
and abrupt bends or displacements ; hence the positions and forms of 
the crystals have been partly determined by the flowing ; and hence, 
also, the rock has not undergone any metamorphic changes since 
solidification took place. Those rocks whose micro-fluidal structure 
is particularly distinct are generally proportionally rich in broken 
crystals shivered into detached sharply angular fragments. Then 
follows a minute classification of the series of rocks. 
The Study of Pycnidia. — It seems that in recent papers by MM. 
Cornu and Bauke an attempt has been made to discover the nature of 
the organs known as spermatia, stylospores, send pycnidia. The two last- 
named organs, since the publication of Tulasne’s Carpologia, have been 
generally admitted to be secondary forms of species of Ascomycetes. 
Certain cases, however, seemed to point to the conclusion that some 
pycnidia were independent organisms, and it was to settle this point 
that Dr. Bauke made his investigations. His method consisted in 
the artificial cultivation of different spores, and resulted in a general 
confirmation of Tulasne’s views. The observations of Cornu have 
extended over several years; and, in regard to the spermatia, he 
comes to the conclusion that they cannot be considered male organs. 
He has observed that they germinate, and thinks that they must 
be regarded as a form of stylospore. Although contrary to the view 
generally maintained as to the nature of spermatia, and to the views 
expressed by Stahl in the ‘ Bot. Zeitung,’ March 20, 1874, Cornu’s 
view coincides with what has recently been published in the ‘ Bot. 
Zeitung ’ and ‘ Comptes Bendus ’ with regard to the supposed sper- 
matia of species of Coprinus by Brefeld and Yon Tieghem. The 
reason why the germination of spermatia has not been seen until 
recently is explained by Cornu by the fact that most cultures of 
spermatia have been made with pure water, whereas the presence of 
some special nutritive fluid, as solution of gum, bark, &c., seems to 
be necessary. Cornu was led to this conclusion by noticing that, 
