28 CRANBERRY DISEASES. 



lobed margin (PL III, fig. IT). It has been found upon the surface 

 of leaves which bore mature perithecia, but was first found on the 

 smooth surface of the upper portion of culture flasks where spores 

 of the fungus had germinated. It is produced at the end of a short 

 germ tube, arising from the ascospore, and its primary function is 

 evidently that of an apressorium or holdfast. 



Appressoria were first described and so named by Fisch 37 in 1882, 

 as found in Polystigma. A little later Frank 38 described the same 

 thing and also the similar productions occurring in Gloeosporium 

 lindemuthianum. These bodies have usually been called chlamydo- 

 spores. Meyer, 39 De Bary, 40 Bu'sgen, 41 and, more recently, Hassel- 

 bring, 42 have discussed these organs and their formation and func- 

 tion. Their production has generally been regarded as due to chemi- 

 cal or contact stimuli and lack of nutriment. The organs which are 

 produced by Acanthorhynchus vaccinii differ in form from any of 

 those described by the authors just mentioned. They have been 

 found, as already stated, on the sides of glass culture flasks and upon 

 the surfaces of cranberry leaves. They are produced in a few hours 

 from fresh spores discharged against and adhering to the cover of a 

 petri dish. These appressoria when transferred to culture media 

 soon germinate and produce an abundance of ascogenous perithecia. 

 They have also germinated on the covers of petri dishes where they 

 have formed. This would appear to indicate that they possess a 

 reproductive function not depending necessarily upon their connec- 

 tion with the surface of the host plant. When produced upon the 

 surface of a cranberry leaf, the small irregular projections about the 

 margin of the disk appear to attach themselves firmly, apparently by 

 dissolving and forming small shallow cavities in the surface of the 

 epidermal wall. A germ tube arises near the center, or sometimes 

 toward the margin of the appressorium, and penetrates the surface 

 of the leaf, usually in the sections we have studied entering through 

 a stoma (PI. Ill, figs. 21, 22). Sometimes the 'germ tube does not 

 appear to penetrate the leaf at once, but sends out several superficial 

 brownish filaments upon the surface of the leaf, as shown in Plate 

 III, figure 20. These appressoria have been frequently found upon 

 fallen cranberry leaves during the summer. They are sufficiently 

 large to be easily observed, and are so firmely attached to the leaves 

 that they are not readily removed. 



Relationship of the fungus. Acanthorhynchus is evidently closely 

 related to certain Sordariaceous fungi, especially such genera as 

 Sordaria and Hypocopra. The perithecia and spores are somewhat 

 similar, and the spores are forcibly discharged from the asci at 

 maturity, as in those genera. In Acanthorhynchus the whole mass 

 of eight spores is thrown in some cases as much as 10 centimeters or 

 no 



