392 COMPARATIVE MORPHOLOGY OF FUNGI 



insect through the unthickened portion of the foot, while the hard integument fur- 

 nishes the necessary support to prevent the fungus being knocked off during the 

 movements of the insect. If the integument is soft, the haustorium may provide 

 additional support as well as nourishment, since it is highly branched and ramifies 

 through the rich, fatty portion of the insect. In part the above series results from the 

 difficulty in technique of carefully dissecting out the rhizoidal portion of the haus- 

 torium, hence figures often give an inadequate impression as to the development of the 

 haustorium. 



The assumption that the food is not rich is incorrect, since the foot is always bathed 

 by the body juices of the insect, and the cells of the fungus usually contain large 

 numbers of fat globules. As in all other cases where a large amount of reserve energy 

 must be stored in a small space, it is stored as fat. They can hardly be called xerophy- 

 tic, since their base is always bathed in a suitable supply of water and they spend most 

 of their life in a humid atmosphere. They are well protected, however, against 

 sudden changes in humidity such as might occur if the host temporarily moved into 

 a drier situation. It is very questionable whether this adaptation has influenced 

 their phylogeny. 



It is also questionable whether they should be regarded as a degenerating group. 

 It is true that they are small, as an adaptation to a highly specialized environment 

 which has also greatly influenced the development of the thallus in other parasites of 

 living insects, but they have a highly specialized thallus in many forms, usually much 

 more highly differentiated than the individual cells in other groups of fungi. 



Without entering the controversy on the derivation of the Ascomycetes from either 

 Florideae or Zygomycetes, certain statements in the argument need correction. 

 It seems just as reasonable to regard the spermatia of Zodiomyces which are often 

 sought out by the trichogyne as spermatia as to regard them as conidia which have 

 secondarily been differentiated as spermatia. In many groups spermatial formation 

 ceases soon after fertilization, and a case like SHgmatomyces Baeri is an exception rather 

 than the rule, in fact it is not a characteristic of this species. Even in the red algae 

 the formation of spermatia is not closely linked with the presence of a mature tricho- 

 gyne on a given individual. 



While as a rule antheridia may arise from either cell of a germinating ascospore, 

 in some groups it is confined to one cell, as in Rickia (the basal). The perithecium 

 usually is developed from the basal cell, but in Coreomyces from the terminal. 



The condition mentioned in Amorphomyces Falagriae is the typical condition in all 

 dioecious forms, although in other respects Amorphomyces is an aberrant type. 

 Since the trichogyne is a very evanescent structure, and since the perithecium grows 

 rapidly after fertilization, eventually the antheridia may be far removed from the 

 mouth of the mature perithecium, yet when young, the trichogyne is usually close 

 to the mouth of the antheridium. In these dioecious types, sex differentiation seems 

 absolute. No instances are known where the females produce antheridia or the 

 males perithecia, even in such unusual types as Dimeromyces adventitiosus, in which 

 antheridia and perithecia are developed, not only in the normal position from the 

 receptacle, but adventitiously from the ordinarily sterile portions of the male and 

 female individual, as the case may be. Unfortunately these forms have not been 

 studied cytologically. 



While Gaumann states that the entomogenous genera of imperfects, like 

 Thaxteriola and Endosporella, may "undoubtedly be regarded" as male plants of 

 Laboulbeniales, he presents no evidence in support of his statement, and such an 

 interpretation seems incorrect in the light of our knowledge of sex differentiation 

 and the discharge of ascospores in all the dioecious groups of Laboulbeniales. 



In the example given of SHgmatomyces Sarcophagae to which might be added 

 Laboulbenia elongata and others, the plants are normally dioecious, and " male individ- 



