856 DR. W. R. M‘NAB. 
the third youngest lateral branch ; and as each new turn is 
given to the apex of the main axis and a new side branch is 
formed, a new transverse septum is produced. Thus a main 
axis is formed, consisting of short twisted cells, each one of 
which bears a lateral branch. ‘The lateral branches may 
behave like the main axis, and form similar secondary lateral 
branches. This, which frequently happens at the early stage 
of growth, is quite exceptional at a later period. The 
primary lateral branches may grow at the apex and twist, 
but without forming secondary lateral branches. ‘The axis 
is thus simply branched, the lateral branches being unlike 
the main axis, and this condition is the rule during the later 
stages of development. The serpentine turnings of the main 
axis may assume a more or less regular spiral form, or may 
grow for some time in one plane, so that the lateral branches 
appear right and left in a bilateral manner. 
As the simple lateral branches of the main axis grow im- 
mediately after their formation close to the apex of that axis, 
and as that apex grows very slowly in length, it becomes 
rather difficult to determine what is a lateral branch and 
what is the apex of the main axis. At a certain stage 
the apex looks as if it divided dichotomously with excessive 
development of one arm of the fork. The apex of the lateral 
branches which remain unbranched becomes curved, show- 
ing that the curving is not caused by the formation of lateral 
twigs. As the branches increase in length their older 
parts increase in thickness. ‘The enlargement is greatest at 
certain parts, so that the thread consists of undivided rounded 
portions, joined so as to look like a row of yeast-cells. 
These swellings follow one another without any appreciable 
isthmus between them. ‘The basal part of each branch, 
however, remains small, like a stalk, bearing the first 
swollen portion (Plate XVIII, fig. 8). Probably from 
eight to ten pear-shaped swollen bodies may develop on a 
branch. 
The unbranched, simple lateral branches are for reproduc- 
tion. Each of the globular swellings becomes an ascus. 
When the swelling is complete a septum forms in the narrow 
isthmus between each of the swellings. As the isthmus of the 
basal part is long, and the septum forms close to the swelling, 
a sac-like projection of the main axis remains. After the 
separation of the swellings the contents of the pear- 
shaped bodies change (Plate XVIII, fig. 9). The uni- 
form contents are broken up by the formation of a large 
central vacuole, which disappears, and in its place several 
smaller vacuoles appear. In the next stage the spores are. 
