Massee. — On the Fungus Flora of New Zealand. 285 



the tissues, and within a very short time form a new centre of 

 disease, producing conidia, which in turn are dispersed and 

 extend the disease. 



From the above account it may be seen how quickly a 

 disease can spread when it has once gained a foothold in 

 places where the host-plant is in considerable numbers and 

 close together, as in a field of corn, in an orchard, forest, &e. 

 These conidia are known as summer-spores, their special func- 

 tion being to enable the fungus to extend its geographical area. 



Towards the end of the season, when the vitality of the 

 host-plant is on the wane, the same mycelium which pro- 

 duced conidia, or summer-spores, now gives origin to a 

 different form of fruit, known as restmg-spores or winter- 

 spores. These spores remain in a passive or resting state 

 until the following season, and germinate at the time when 

 the host-plant is pushing into active life. The function of the 

 resting- spore condition is to secure the continuation of the 

 species, by tiding it over that portion of the year when the 

 host-plant is not in active growth. 



In addition to the production of resting-spores, the mj'^- 

 celium of many species of Fungi becomes concentrated into 

 a number of compact masses or nodules, called " sclerotia." 

 usually of a black colour externally. These sclerotia, which 

 vary in size in different species from that of a pin's head to a 

 cricket ball, also remain in a quiescent state during the 

 winter, in the tissues of the leaves or stem where they are 

 formed, or in the ground, and in the following spring produce 

 reproductive organs, which infect the young leaves of the host- 

 plant, and commence anew the cycle of development. 



From the above account it will have been gathered that 

 resting-spores, or sclerotia, give origin to the disease in the 

 first instance by inoculating the host-plant, the spread of the 

 pest being afterwards secured by the rapid production of 

 summer-spores. Although the leaves or stems bearing rest- 

 ing-spores or sclerotia may completely decay during the 

 winter, the reproductive parts of the fungus do not perish, 

 but remain lying on the ground until the host again makes its 

 appearance, and then act as already described. The resting- 

 spores on the straw of cereals do not fall away readily. The 

 corn may be harvested, the straw used for fodder, pass on to 

 the manure-heap, be returned to the land as manure, and yet 

 the resting-spores may be found attached to fragments of the 

 decaying straw, and quite capable of germination. Finally, 

 resting-spores and sclerotia often possess the power of re- 

 maining in a dormant condition for several years, thus extend- 

 ing the means for continuing the struggle for the sm'vival of 

 the fittest, often much to the disadvantage of the farmer and 

 horticulturist. 



