Conjugate Nuclei in the Ascomycetes. 
BY 
E. J. WELSFORD, F.L.S., 
Assistant in the Department of Plant Physiology and Pathology , Imperial College of 
Science and Technology. 
With four Figures in the Text. 
D URING the last few months an investigation of the process of 
infection by Botrytis cinerea has revealed the fact that the nuclei in 
the multinucleate hyphae of this fungus, produced by the germinating 
conidia, are very generally arranged in pairs. Such hyphae were very 
well nourished, having developed at a temperature of 26° C. either in 
strong turnip juice or in the tissues of the leaf of Vicia Faba . Mycelia from 
conidia grown in water or much-diluted turnip juice (i in 16) did not show 
paired nuclei, neither were these found in the narrow ill-nourished hyphae 
which occasionally occur in the parasitic mycelium in the Bean leaf. The 
paired condition of the nuclei is only found in well-nourished fast-growing 
filaments, and hence it seems to be correlated with rapid growth. The 
pairing can be explained by the fact that nuclear divisions follow one 
another so rapidly that the sister nuclei formed by one division have 
not time to move apart to any considerable distance before they start 
dividing again. 
Fig. i is a drawing of a conidium growing in strong turnip juice; 
all the nuclei are in the paired condition ; the members of the pairs in 
the germ tube are farther apart than those in the conidium ; the separation 
is no doubt preparatory to division. An older stage is shown in Fig. 4 ; 
only part of the hypha is drawn ; it had entered its host plant and was 
thriving on nourishment obtained from the epidermal cells. The pairs 
of nuclei marked a have recently divided, those marked b have no doubt 
moved apart in preparation for further division. The fact that an unpaired 
nucleus is rare in a well-nourished filament indicates that the sister nuclei 
divide simultaneously. A striking contrast to these well-nourished hyphae is 
shown in Figs. 2 and 3. Fig. 3 represents a germinating conidium twenty- 
four hours after sowing in a drop of distilled water on a glass plate ; the germ 
tube which can only draw nourishment from the conidium has very few 
[Annals of Botany, Vol. XXX. No. CXIX. July, 1916.] 
