658 Fritsch . — Two Fungi , parasitic 
attributed the fact that the Fungus so frequently leaves 
the main filament for a branch at the points, where branching 
of the Tolypothrix occurs ; it thus avoids the heterocyst, 
which is situated immediately above the point of branching. 
A few anomalous cases were observed in connexion with 
the external mycelium. Thus Fig. 12 shows a hypha which 
has just emerged and has formed a number of branches, one 
of which is again penetrating into the same algal filament, 
whilst Fig. 15 shows a case where the mycelial branch has 
re-entered the Alga and fused with the hypha from which it 
arose. 
I have already mentioned that the external mycelium may 
be very much branched. In some cases it attains a great 
development and proceeds to form large numbers of spores. 
The mycelium then becomes septate and develops numerous 
lateral branches, which generally do not reach any con- 
siderable length. In these branches transverse walls are 
formed, so that they come to consist of a row of thin-walled 
cells. These increase in size, at the same time assuming an 
elliptical shape (Fig 16), and develop into the thin- walled 
spores, which were first seen in November last. In some 
cases the lateral branches are very short and only develop 
into a single spore, which is thus formed in a way very 
similar to the chlamydospores of the first described species. 
In other cases the mycelium proceeds to form these spores 
immediately after emerging from the Alga, as is seen in 
Fig. 17 ; here the entire external mycelium has been trans- 
formed into spores. This is frequently the case, and when 
spores are thus formed from a strongly-branched and ex- 
tensive mycelium we get enormous masses of them, many 
of which still show their origin from a row of cells. The 
spores are oval and generally slightly drawn out at one or 
both ends, owing to their previous position in a moniliform 
thread (cp. Fig. 16). When occurring in extensive masses 
the shape of the individual spores is often very curious, 
probably owing to mutual pressure in their crowded position. 
These spores can germinate almost at once, sending out one 
