32 PROCEEDINGS OP THE AMERICAN ACADEMY 



It will be well before speaking of the spermogonia themselves to 

 give a brief description of the hyphse of the fungus as they appear 

 in the host plant. Before the spermogonia have begun to develop, 

 a section of the affected leaf of the Rubus shows the presence of 

 hyphse, which ramify through its tissues, without, however, pro- 

 ducing any very great distortion in the cells. The hyphse are of a 

 pretty uniform diameter, and, while at first almost simple, later be- 

 come considerably branched. They do not seem to traverse the cells 

 themselves to any great extent, if at all, making their way rather 

 between adjacent cells and in the air spaces of the leaf. They 

 do, however, send into the cells curious haustoria which present a 

 very characteristic appearance (Tigs. 5 and 9) already figured by 

 Newcomb and Galloway.* At the places where these processes 

 pass through the cell walls they are contracted to a very much 

 smaller diameter than the ordinary hyphse, but inside the cavity 

 of the cell they become very much expanded, and often curiously 

 knotted. A few characteristic forms have been figured (Fig. 9, 

 a, b, c). The haustoria were more noticeable in the material which 

 had been collected later in the season than in that gathered before 

 the spermogonia were to be seen. 



In the region immediately below the epidermis, the hyphse are 

 very much more thickly massed than in other portions of the leaf, 

 having forced their way in between the epidermal cells and the 

 parenchyma beneath. In this locality, and also to some extent 

 elsewhere, it may be demonstrated by proper staining that the 

 hyphse are septate, especially after the formation of the spermogo- 

 nia. In fresh material the contents of the hyphse are largely hya- 

 line, only occasionally showing a finely granular appearance, and 

 many vacuoles are to be seen. As has already been said, the hy- 

 phse themselves do not excite any marked morbid growth in the 

 tissues of the leaf, but in the immediate neighborhood of the 

 spermogonia there is a very considerable distortion. In leaves 

 that are at all badly affected by the fungus, the chlorophyll very 

 generally changes its color, becoming yellowish or brownish, so 

 that the infected portions are very noticeable on the growing plant. 

 In such cases the whole contents of the epidermal cells, as well as 

 the chlorophyll grains, have disintegrated more or less, particularly 

 in the immediate neighborhood of the spermogonia. 



The first indication of the formation of a spermogonium is seen 



* Journal of Mycology, Vol. VI. p. 106, PI. VI., 1891. 



