86 Cayley. — Some Observations on the Life-history of 
cell of one spore to that of another has never been observed, but frequently 
one cell is seen to contain two nuclei, and the cell to which it is linked is 
enucleate (Fig. io b). Also, one or all the cells of a macrospore, when 
mature, have often been seen to contain two nuclei, but this was thought 
to be due to the division of the primary nucleus (Figs, io a and 12 a). 
Macrospores which are quite free and unlinked can have binucleate cells 
(Figs. 10 a and 12 a). It is not easy to suggest what this peculiar behaviour 
indicates. At first it was thought that in Nectria , since the perithecia 
arise on the same sporodochium as the summer macrospores, this fusion of 
macrospores might possibly be a sexual fusion from which the perithecia 
eventually arise. There is, however, no proof of this supposition. The 
fungus is so small, and the mycelium of the sporodochium so twisted and 
dense, that in spite of prolonged search it was found impossible to trace 
the origin of the mycelium or cells from which the perithecium arises, or 
to find any definite connexion except one of position. 
Variation in size and shape of the ’ mature macrospores has been 
described and figured by previous workers in Nectria and other forms of 
Fusarium (Fig. 13 a). One or more cells in the middle of the spore can 
become enlarged, with thickened walls and deeply staining rich cell 
contents ; also bodies were observed by the author among the macrospores 
on a well-developed sporodochium, consisting of a stalk cell and three to 
four enlarged circular cells, the terminal or penultimate cell of which 
contained rich cell contents. These bodies certainly did not give the im- 
pression of being degeneration forms, but it is impossible to say whether 
they perform any special function. Lapine thought the enlarged central cells 
of the macrospore to be of the nature of chlamydospores, but Aderhold, 
on the other hand, considered them to represent degeneration stages. 
Perithecidl Stage. 
The perithecium arises from a tangle of coiled hyphae (Fig. 23), which 
appear to branch off from the thick- walled sporodochial mycelium. No 
differentiated archicarp has ever been observed to which the perithecium 
could be traced. The sporodochium forms a thick and complex layer of 
twisted hyphae with walls of varying thickness, and it is not possible to tell 
Avhich particular knot of hyphae will eventually develop into a fertile 
perithecium. Sterile perithecia-like bodies occur both on bark and artificial 
media ; they consist of the usual outer layers of brown, thick-walled, deeply 
staining mycelium, enclosing the thinner-walled hyphae with uninucleate 
cells. The nuclei of these central cells soon disappear and no further 
development occurs except increase in size. Schaffnit ( 27 ) observed similar 
bodies in Fusarium nivale and considered them to be sclerotial organs. 
Not infrequently, however, one or more small fertile perithecia have been 
