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Perithecial development in Nectria mammoidea, Phil. et Plowr; also, the study of Nectria mammoidea, Phil. et Plowr. in culture, with an account of the factors influencing perlthecial production in the genus; and, The parasitism of Nectria cinnabarina (Tode) Fries.

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McIntoshAES_1927redux.pdf (39.39Mb)
Date
1927
Author
McIntosh, A. E. S.
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Abstract
 
 
The paper deals with the development of the perithecium in Nectria mammoidea. Phil, et Plowr.
 
The cells of the vegetative hyphae are multinucleate.
 
The perithecial initial is a knot of vegitative hyphae, and at its inception and throughout its development no trace of a structure or structures resembling archicarps can be seen.
 
The appearance and development of structures provisionally termed "interpolated" is described and it has been found impossible to homologise them with known existing structures in the ascocarps of other As corny ce te s. These structures disintegrate prior to the appearance of the ascogenous hyphae.
 
These latter arise de novo from the cells lining the base of the perithecial cavity. They are simple binucleate structures and are not separated by a cell wall from their parent hyphae, but are merely prolongations of the latter. Without proliferation of these hyphae or division of their two nuclei, the latter fuse to give the definite ascus nucleus.
 
The ascus grows and is a prolongation of the parent ascogenous hypha.
 
The definite ascus nucleus divides three times, one reduction division only taking place.
 
The spores are formed from the ascus cytoplasm by a free cell formation.
 
The spore nucleus divides and a wall separates the two daughter nuclei which thus each occupy a cell in the spore. The latter becomes invested by a spore wall.
 
The grosser features of the perithecial development are described throughout the account in the sequence of their occurrence in development.
 
Pycnidia were not found in culture but structures which may be sterile perithecia were seen on a few occasions.
 
- - - - - - -
 
The variation in the literature dealing with observations on the parasitism of Nectria cinnabarina (Tode) Fries, is reported in the Introduction.
 
These variations are concerned chiefly with two points in the parasitism of this species viz:- (a) the part of the host tissue primarily attacked, and (b) the reaction of the host to attack]
 
The case of this fungus causing a canker of apricot, and the various symptoms observed are dealt with.
 
With a view to trying to throw some light on the reason or reasons for this symptom variability in the host, cultural studies and inoculation experiments were carried out with two strains of the fungus (1) a strain from the beech, and (2) a strain from the apricot.
 
The two strains were found to be separable on a cultural basis, while it appeared from inoculation experiments, that the beech strain might be a more virulent parasite of the apricot than the apricot strain. The latter was shown to be the cause of a canker on the apricot.
 
It was concluded that, as seen in the Introduction, this fungus was capable of causing a variability of symptoms in its host plant. The investigation indicated that this latter might be due to the existence of physiological strains in the species, or be the result of the varying ages of the host parts attacked.
 
A more extensive series of inoculation experiments than that carried out during this investigation, would probably decide which of these two factors was the causative one. Both, however, may be concerned.
 
URI
http://hdl.handle.net/1842/35244
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