258 STATE HOETICULTURAL SOCIETY. 



The rapid propagation of some of our higher plants by runners, 

 bulbs, root-cuttings, or other non-sexual method, is similar to the pro- 

 pagation of fungi by these non-sexual or summer spores. 



The sexual spores are the result of a special sexual process, fully 

 described by Scribners, DeBary, Halstead and others. These spores 

 have thicker walls, they live over vs^inter, and are capable to start the 

 cycle of life anew the year following. I shall now try to describe the 

 spore forms of a few of the most injurious parasites. 



Apple-scab f Fusieladeuni dentriticum). — As I have written a paper 

 on this fungi for this meeting, I will simply state here that the spores 

 germinate at a temperature of about 50^ F., according to Scribner. 



BiTTER-ROT f Oloesporium friietigenum). — This parasite I have not 

 got in my orchard, and did, therefore, not have the chance to study it 

 closely, but from what I have seen of it in neighboring orchards, and 

 from what I have learned through Scribner and Galloway, would say 

 that it is usually reproduced by non-sexual or summer spores in the 

 following manner: The spores are born singly upon the tips of closely 

 compacted threads. It was found that they will germinate in water 

 in about 10 hours, which would indicate a rather low temperature; if, 

 therefore, the spores find a lodging place upon young apples, and the 

 proper conditions are present, they will germinate by sending out a 

 germ-tube, which penetrates quite deep into the tissues of the fruit, 

 where a new plant-body will be established. These will continue to 

 enlarge until it breaks through the cuticle, thus forming the spots 

 known as bitter-rot. 



The Downy and Powdery Mildews are parasites which are caus- 

 ing fruit-growers a great deal of trouble. There is a great difference 

 in the life histories of these two parasites. Conditions favorable for 

 the development of one are to a great extent unfavorable for the 

 other, and, as they often prey upon the same host, as in the case of 

 the grape, it is very important that the conditions necessary for their 

 development were better understood. 



Downy Mildew fPeronospora riticola, D. By.j — The vegetative 

 portion of this parasite grows between the cells of the leaves, fruit 

 and young shoots; little suckers, known to the botanist as hausteria, 

 penetrate the cells for nourishment. In the leaves it usually occupies 

 the lower or loose and irregular cells. The slender, thread-like fila- 

 ments of the fungus always issue through the breathing pores on the 

 under side of the leaves in very large numbers, firing the downy white 

 patches. These filaments are more or less branchal, and produce a 

 non-sexual spore known as conidia. Scribner says that from two to six 

 millions of these spores may be produced on a single vine. These 



