Nov. is, 1920 Crownwart of Alfalfa Caused by Urophlyctis alfalfae 307 



in a miscellaneous manner over the surface of the resting spore by the 

 enlargement of the latter. 



The time of proliferation of the resting spore seems to be rather vari- 

 able. It may follow immediately after the septum delimiting the last 

 peripheral segment has been laid down, before the proliferation of the 

 new order of turbinate cells has begun (PI. 48, B, rb), or more usually 

 somewhat later when one or more of the peripheral segments have pro- 

 liferated secondary turbinate cells (PI. 48, C, rb). Or, as is not infre- 

 quently the case with the unusually large primary turbinate cells, the 

 immediate product of infection, the resting spores may not be formed until 

 three or four successions have intervened and the original lesion has be- 

 come a well-developed cavity (Pi. 50, tba). The protoplasm in the spo- 

 rogenous cells of such primary turbinate structures as well as the host 

 protoplasm of cells or cavities that have long harbored the fungus fre- 

 quently take a dense uniform stain with safranin — a result that might 

 readily be attributed to the diffusion of a deep-staining substance. 

 Where this abnormal condition becomes very pronounced, it is not im- 

 probable that no resting spore is produced at all, the deep-staining 

 protoplasm finally disintegrating in place. With perhaps this occasional 

 exception, every turbinate cell produces always one resting spore. Ac- 

 cording to Maire and Tison (21), Urophlyctis hemisphaerica (Speg.) Syd. 

 produces first a succession of "vesicules collectives," each of these in 

 turn giving rise to several others of the next order, until ultimately 

 each "vesicule collective" produces only a single resting spore. Such 

 separation of vegetative and reproductive stages is not discernible in U. 

 alfalfae, the production of resting spores being common to each order 

 of turbinate cells; and, although toward the end of the season, when 

 conditions for growth become poor, the proliferation of turbinate cells 

 may be considerably reduced, as may be inferred from the relatively 

 small number of young conditions in old galls containing an abundance 

 of mature resting spores, it is questionable whether their production is 

 ever entirely stopped so long as the host tissue is alive and growing. 



In this connection it may be mentioned that the presence of unfavorable 

 conditions for development is indicated usually by a very pronounced 

 enlargement of the hyphae. When the parasite is growing vigorously the 

 hyphae, by which the youngest turbinate cells are attached, do not ordi- 

 narily exceed 0.5 ll in diameter. Tater their diameter ordinarily increases 

 to 0.8 to 1 fi, the increase being, as Vuillemin (35) has pointed out, in 

 the wall, the lumen remaining the same and, indeed, soon appearing 

 devoid of protoplasmic contents. In old, overwintering galls, however, 

 there may be found usually an abundance of hyphae measuring 3 to 

 5 /x, the surface of which may be marked with irregularities which give 

 the structure a granular appearance, especially in stained paraffin sec- 

 tions. Within these hyphae the turbinate cells occur as loculi in dis- 

 tensions occupying junctional or terminal positions and are connected 



