SECTIONAL TRANSACTIONS.— K. 613 



Prof. F. L. Stevens. — On the Effects of ultra-violet Light on Fungi, with 

 special reference to Sexual Reproduction. 



In January 1928, while studying the effect of ultra-violet radiation on fungi in 

 agar plate cultures, it was noticed that perithecia were present in large numbers on 

 certain portions of the exposed plates. The fungus was a strain of Olomerella cingulata, 

 which had been under close observation for several months, had been originally derived 

 from apples affected with Bitter Rot, and from which a single conidium had been 

 isolated. All cultures secured from this monosporous source had been devoid of 

 perithecia. This same essentially non-sexual strain in all agar cultures exposed to 

 ultra-violet rays of certain intensity and for certain duration has produced perithecia 

 in large numbers. No perithecia have appeared in the non-radiated portions of the 

 cultures. The most striking evidence that the radiation induces perithecial formation 

 was given by projecting the rays through a circular aperture of 0-5 mm. diameter 

 upon a susceptible colony. On this area alone perithecia appeared two days after 

 radiation. In four days asci and spores were formed. The perithecia differ from 

 those normally found in that they are spherical and non-stromatic, but the asci and 

 spores agree with those found in nature. All other strains of Olomerella tested have 

 given similar responses to ultra-violet light. It appears certain that ultra-violet 

 rays or others near them greatly accelerate conidial formation in this and other 

 genera of fungi, as for example has been observed to be the case in Coniothyrium, 

 which produces numerous pycnidia within a few days under radiation instead of after 

 several weeks as under natural conditions. It is held that direct radiation has resulted 

 in the formation of perithecia deeply buried in the agar, while indirect rays have 

 led to the formation of superficial perithecia. That the effect is not the result of a 

 chemical change produced in the medium by radiation, but is a direct response by the 

 mycelium to radiation, is considered probable by experiments directed to this special 

 question. 



Mrs. N. L. Alcock. — Seed-home Clover Sickness (with an introduction by 

 Mr. T. Anderson). 



The following matters are discussed : 



The importance of quality, health and source of seeds generally. 

 Clover seed and the country of origin. 



A case of Sclerolinia disease carried in the seed of New Zealand clover. 

 The life-history of the fungus isolated from the seed from the resting mycelium 

 to the apothecial stage. 



The question of re-infection of various clovers. 



The comparative freedom of wild white clover from disease. 



Miss M. J. F. Wilson. — A Comparative Study of Dermatea spp. on 

 Conifers, with some Observations on the Conidial Stages. 



In this investigation an attempt has been made to define the limits of the species 

 bj' a comparison of morphological and physiological characters. The principal point 

 of distinction between the various fungi is ascospore size, and when a difference in 

 this feature is correlated with differences in the conidial stage and in cultural characters 

 the organisms have been regarded as separate species. A biometric study of spore 

 measurements has been made, and the results up to the present time show that five 

 distinct species exist, only two of which have previously been described. The conidial 

 stage of these fungi is a Myxosporium which produces two types of spore, large oblong 

 conidia and minute rod-shaped bodies which do not germmate. The conidial 

 fructification is at first a closed pycnidium, but later the upper wall breaks down 

 entirely. 



Mr. G. G. Hahn. — Life History Studies of the Species of Phomopsis occurring 

 on Conifers. 



A study of coniferous Phomopsis forms which includes all the present known 

 species, as well as undescribed species, has been undertaken to investigate their 

 cultural life-histories. This research has been associated with an investigation of 

 Phomopsis Pseudotsugae Wilson, an economically important parasite of the Douglas 



