3^59 



cully how fit a point it is for parasitic attack. Here, under the skhi, 

 formed of plate-like cork cells (k) (in the subjoined Fig. 53), we find the 

 first stages of lenticel formation beneath the stomata in the form of irregu- 

 lar cells, poor in contents (a). Since this cell formation extends further 

 and further backwards and the cells first formed take up water, swell and 

 rupture the corky cortex, a lenticel is produced which now gives rise to 

 scurvy. From it the loosened cork cells (/) push out in the form of a 

 whitist, moist meal. These cells decay, and the process of decay is con- 

 tinued further inward so that the close pressed, still connected rows of 

 immature cork cells (v) must be sought deeper and deeper in the interior 

 of the tissue. Here the starch (^0 disappears from the tissue surrounding 

 the cork cells. Continued moisture will develop very similar conditions in 



Fig. 53. Identical formation on the potato sliin. 



other underground parts of plants. In this process the cork mantel, which 

 has previously acted as a protection, is seriously loosened and broken apart. 

 The scurvy disease has recently been considered to be parasitic and 

 usually is described as due to bacteria. Therefore, it is also treated in the 

 second volume of this manuaP. But there it is emphasized, that the cause 

 is ascribed to very different organisms, by some, to bacteria, and by some 

 to fungi. On the one hand, it is stated that these organisms should be con- 

 sidered as wound parasites, which cannot attack the uninjured cork layer 

 (Kriiger), while, on the other hand, inoculation experiments on immature 

 organs have been carried out successfully under special circumstances. 

 (Bolley). It must also be added here that a great many practical experi- 

 ments have determined beyond question that, as already mentioned, certain 

 substances contained in the soils favor scurvy. This explains the possible 



1 See Beet scurvy, p. 46 and Potato scab, p. 75. 



