38 



BLOSSOM INFECTION IN MELANDRYUM. 



The smut forms already described appeared in the blossoms of grasses: that is, of plants 

 characterized by wind fertili::ation. There are, however, a number of smut fungi which occur 

 in plants fertilized by insects and which attack separate parts of their blossoms. An especially 

 characteristic form of this kind is given in the anther smut, which appears chiefly in the blos- 

 soms of the Caryophyllaceae. The infected host plants appear externally absolutely normal, 

 the anthers alone are attacked by the smut fungus, Vstilago anthcrarum or Ustilago violacea^. 



Instead of pollen grains, as in normal anthers, thick spore masses with violet spores are 

 found in the pollen sacs here. The spore masses are very abundantly formed and pushed for- 

 ward from the place of formation in such quantities that the anthers rupture, exposing the 

 spore masses. The spores are not as dusty nor as easily disseminated as those of the loose 

 smut. They have a rather sticky nature, such as belongs to the pollen of plants fertilized by 

 insects. If, for example, the blossoms of Mclandryum album infected with anther smut are 

 observed for several days at the beginning of their time of flowering, it will be seen that influ- 

 ences are felt here which force the spores out of the anthers. The white inflorescences look as if 

 soiled by clinging smut spores. It is by this means that anther smut usually makes itself known 

 outside of the attacked blossom. The blossoms of Melandryum album open in the evening and 

 remain open in the dark. They are visited by insects, especially night-flying butterflies, which 

 stick their probosces into the blossoms, in order to suck the honey. In this way spores of the 

 smut are forced out simultaneously, thus soiling the white inflorescences with the dark smut 

 spores. When convinced of this fact, one understands involuntarily that the forcing out of 

 the smut spores from the anthers of the infected blossoms is brought about by the butterflies. 

 The infection, that is, the distribution of the smut disease, therefore is not brought about here 

 by the zvind, but by insects which fertilize the blossoms. The insects which have visited a 

 smutted blossom carry over to the stigma, the style and the young ovule of neighboring pistil- 

 late blossoms, the smutted spores sticking in masses to their probosces, so that infection can 

 take place by means of insects in the simplest and most natural way from staminate blossoms 

 to pistillate blossoms in these dioecious declinous plants. If the investigator assumes the 

 role of this insect and carries the anther smuit to the pistillate blossoms as does the proboscis 

 of the butterfly, he is easily convinced that the smut spores, carried to the inner parts of the 

 pistillate blossom, where they come in contact with stigma secretion and honey, the most favorable 

 substrata for their saprophytic nutrition, germin ate most easily here and indeed in the forms 

 described for anther smut in Part V of this work. Nothing stands in the way of the hypothesis 

 that the germ tubes, growing out from single or fused conidia and resembling pollen tubes" 

 strikingly in their form, can like these grow through the canal of the style, penetrate into the 

 ovule and, reaching the eggs on the central placenta, can infect them there. Like a flash of 



(1) Undoubtedly the whole plant Is here attacked by the fungus of the Anther smut, which occurs 

 constantly on all blossoms of the much branched plant. 



(2) Compare the illustrations on plate I, Part V, of this work — figs. 25-27. 



