230 THE ENTOMOLOGIST. 



these there are no signs ; the only things at all resembling stride 

 are the wrinkles seen on the peridium of the fungus of P. rapcB and 

 P. napi; moreover the stem separates from the peridium at a certain 

 definite spot, where there exists a sort of " hilum." If the fungi 

 were connected with the butterfly's wing by these bulb-like bodies, 

 a large proportion of them would fall off, and the butterfly would 

 lose whatever benefit these so-called androconia afforded, the 

 bulbs remaining attached to the wings as useless incumbrances. 

 On the other hand, assuming these bulbs to be sporocarps of a 

 fungus, what more natural than that they should fall off after 

 they had completed their work of maturing and shedding their 

 spores ? 



Again, if these organisms are only modified hairs or scales, 

 they would be formed of chitinous material. The fungus of 

 P. brassiccE generally has the stem bent to a considerable angle 

 with the body (peridium), but on adding a drop of water the 

 stem straightens out. I submit that if the material was chitine 

 it would not exhibit this sensitiveness to moisture. But this is 

 not all ; the sporocarps from dry examples of P. raim and P. napi 

 have a "withered" appearance, the addition of a little water 

 causes them to swell, the wrinkles disappear, and the black spot 

 so conspicuous on the apex of the fungus of P. agathina (p. 171) 

 makes its appearance. I repeat that the withering and sub- 

 sequent "plumping" out on the addition of water indicates a 

 vegetable and not a chitinous substance. 



But if up to this point I had felt any doubt as to their 

 character, all doubts would have been entirely dispelled on 

 seeing the wonderful parasite of Pieris agathina (see p. 171). 

 Here, again, the sensitiveness to moisture is noticeable. When 

 they are first removed from the wing about one-fourth the 

 length of the basal portion is bent so as to form an obtuse 

 angle with the axis of the body, giving the fungus an unsymme- 

 trical appearance; but after keeping them between glass sKps 

 for a day or two, the dampness of the room causes them to 

 straighten out and assume a perfectly symmetrical form. It was 

 the observation of this fact that induced me to add the note on 

 p. 171 relative to the probable origin of the square form of this 

 fungus. A comparison of the " glassy" sporocarp of this fungus 

 with that of the fungus of P. ra^m (after damping the latter) will 

 convince anyone of their identity of form and function ; and as 

 the parasites of all the Pierids mentioned are closely allied, the 

 demonstration of the apex of one form settles it for all the others. 

 It should be borne in mind that what we see on the butterfly's 

 wing is merely the fructification of a plant whose vegetative 

 organs (mycelium, &c.) are enclosed within its substance. I 

 may also state that the spores of the hrassicce fungus germinate 

 freely between slips of glass. 



The circumstance of their occurring only on male butterflies 



