384 



COMPARATIVE MORPHOLOGY OF FUNGI 



with a wall firmly attached to the inner surface of the wall of the mother 

 cell. This small cell which ultimately becomes the basal cell of the append- 

 age then perforates the wall of the mother cell, growing outward through 

 it by a narrow extension of its protoplasm, which, finally reaching the 

 outer surface, forms there a walled prominence from which the appendage 

 is organized. 



In some species of Ilytheomyces, (Thaxter, 1917) Chitonomyces and 

 various other unrelated genera, "trigger" organs develop in positions which 

 affect the tension within the perithecium, on contact with another host 



Fig. 259. — 1. Chitonomyces longirostratus, showing tip of perithecium highly developed 

 a-nd functioning as a trigger organ. 2. Chitonomyces oedipus, showing trigger organs. 3. 

 Chitonomyces japanensis. 4. Chitonomyces introversus. 5. Chitonomyces ceroiculatus. 

 {After Thaxter, 1924.) 



or any firm object, in such a manner as to induce a sudden discharge of 

 spores e.g., C. oedipus, C. japanensis, etc. (Fig. 259, 2 to 5). In Chito- 

 nomyces longirostratus (Fig. 259, 1) the cells of the perithecial tip are 

 elongated into a slender, indurated tube. At the impact with another 

 host, slight bending of the tube will produce a very great compression 

 of the perithecium and cause an immediate ejection of spores while the 

 chance of infection is greatest. With the degeneration of the ascus as 

 a mechanism for violent discharge, its function seems to have been 

 assumed by the whole perithecium. 



In Trenomyces, the basal cell of the receptacle directly penetrates 

 the host without the formation of a differentiated foot, although this 

 region may sometimes be colored. The intruded rhizoid swells more 

 or less abruptly beneath the integument, so that the individual is firmly 



