26 



Bulletin 125. 



growth progresses outward the mass brakes through the epidermis of the 

 host, and appears as a pink cushion on the surface of the stem. A longi- 

 tudinal section through one of these when examined under the microscope 

 presents the appearance represented in the figure. The long, spreading 

 mycelial threads may be seen coursing through the layers of the bark forc- 

 ing the cells apart. In the tubercle itself the threads are broader and much 

 septate by cross partitions, so that the mass thus formed resembles a tissue 

 composed of narrow elongated cells. Toward the top of the tubercle the 

 filaments are more compacted and thread-like. At the surface they become 

 separated from one another and sparingly branched, each bearing small spores 

 or conidia at its apex, and on very short branches or stigmata along its 



sides (Fig. 5). These conidia are exceedingly small 

 measuring only 6-S/j. long by 3/7. wide. They are 

 narrowly elliptical in outline and colorless. Im- 

 mense numbers of conidia are borne on each tuber- 

 cle, and, being so small and easily detatched, are 

 scattered widely by the wind, thus forming a very 

 efficient means of spreading the disease. Each 

 conidium is capable of germinating under favora- 

 ble conditions of temperature and moisture. The 

 slender tube thus produced enters the tissues of the 

 host, where it elongates and branches producing 

 an abundant mycelium. 



The perithecia found on one of the canes were 

 not fully mature, but were sufficiently so to admit 

 of the determination of the species as Pleonectria 

 berolinensis, Saccardo. This was afterward found 

 to be a separate fungus in no way connected with 

 the Tubercularia. All of the canes collected on the 

 trip were planted in the leaves and humus in one 



HyphcE of Tuber- ^^ ^^^ nearby ravines, in the hope that more of the 

 cularia bearing . , . , / , , , , , 



conidia penthecial forms would be produced. 



The History of the Fungus. 



The Tubercularia vulgaris is a very common fungus which has long been 

 known as a saprophyte growing on dead and decaying branches. Nearly all 

 of the deciduous woody plants are numbered among its hosts, the genus 

 Ribes^ to which the currant belongs, being a favorite in this respect. It has 

 passed under many names according as the forms on the various hosts were 

 regarded as belonging to the same or distinct species. In 1865, Tulasne 

 (Selecta Carp. Fungorum, III), united all these forms under the old name 

 Ttibercularia vulgaris, Tode, and gave numerous drawings and facts to prove 

 its connection as an imperfect stage with the very common ascomycetous 

 species, Nectria cinnabarina, (Tode) Fr. That this connection exists is 

 evident, so that the fact has since stood unquestioned. In regard to the 



