198 SECTIONAL ADDRESSES. 



tests, a distinction can be drawn between (+) and ( — ) strains, the former, 

 like the female plants of dioecious angiosperms, being the stronger reducers. 

 It may be suggested, as a working hypothesis, that nutritive heterothallism 

 arose in the ancestors of the higher fungi after their mycelium had become 

 septate, and was made possible by the prevalence of mycelial fusions 

 which distinguishes septate forms. 



Sex and Nutrition. 



But, after all, if heterothallism in these fungi is a nutritive phenomenon, 

 does it thereby differ from sexual fusion ? Van Rees^^ in 1887 and 

 Dangeard^^ in 1899 suggested that syngamy first arose as a process of 

 reciprocal cannibalism or autophagy. Gametes were characterised as 

 hungry cells which lacked the means to continue their development 

 unaided, and were able to do so only when two had pooled their resources. 

 Thus we have the facultative gametes of Ulothrix, which function as zoo- 

 spores when conditions are good, and the gametes of Synchytrium, which 

 are zoospores retarded in development. In Reticularia Lycoperdon, Wilson 

 and Cadman®*^ have shown that, after the union of two gametes, three to 

 eight similar swarmers are drawn into the mass and coalesce ; their nuclei 

 degenerate and they serve as food, but the process in its early stages is 

 very like the gametic union. Syngamy may be, in fact, in some of its 

 aspects, a form of nutrition, but that is very far from saying that all 

 forms of nutrition are syngamy. The fungi, in addition to the wide 

 variety of their sexual process and their many saprophytic and parasitic 

 means of obtaining food, have given evidence of a special development 

 which, partaking of some of the characters of each, may possibly throw 

 light on the peculiarities of both, and, in so doing, may provide a clue 

 to the significance of the primitive sexual fusion. 



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4. Barrett, J. T., Ann. Bot., xxvi, 1912. 



5. Loewenthal, W., Arch. f. Protistenk., v, 1904-5. 



6. Wager, H., Ann. Bot., xxvii, 1913. 



7. Klebs, G., Jahrb. f. wiss. Bot., xxxiii, 1899 ; Coker, W. C, The Saprolegniaceoe, 



U. of N. Carolina Press, 1923. 



8. Coker, W. C, loc. cit. 



9. Ashby, S. F., Kew Bull, ix, 1922. 



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