36 



It is probable that a slight difference in the acidit}' of the paren- 

 chyma in different varieties of hyacinths is what renders some varieties 

 more vsusceptible than others, but this can not be settled without fur- 

 ther experinients which were best undertaken in the Netherlands, 

 where according to Wakker the growers have long recognized that 

 there are susceptible and nonsusceptible varieties. 



The reader will be better able to judge of the correctness of these 

 conclusions after reading Bulletin No. 2<S in which the cultural pecu- 

 liarities of this organism are discussed and compared with those of 

 Ps. campestris, Ps.pliaseoli, and Ps. stewarti, three other 1-flagellate, 

 j^ellow bacteria common in the United States. 



MORPHOLOGY OF THE PARASITE. 

 SIZE AND SHAPE. 



This organism is a medium-sized slender rod, multiplying b}' fission. 

 The ends are rounded. It is slightly variable in breadth and, under 

 certain circumstances, greatly variable in length. Indeed, according 

 to varying external conditions the length may be said to fluctuate 

 enormoush'. Many examinations and measurements have been made. 

 In the plant and in exhausted culture media it is generally only a 

 single rod 1^ to 2 times as long as broad ; rarely more than twice as long 

 as broad. The appearance of some of the rods, which were taken 

 from the daughter bulb examined in February, 1808, is shown in Plate 

 I, fig. 8«. On slides stained 5 minutes in a saturated watery solution 

 of basic fuchsin the}^ were 0.4 to 0.5 by 0.5 to 1.0 //. From the interior 

 of a bulb of the first series (the slide stained June 23, 1807, in Avaterj^ 

 solution of basic fuchsin and mounted in Canada balsam and measure- 

 ments made August 8, 1808), they were O.o by 0.0 to 1.5 //, most of the 

 rods on this slide being 0.5 by 1.0 to 1.2 /.i. Taken from fresh cultures 

 in beef broth they are a little longer. Plate I, fig. Sh shows tj^pical 

 forms from an alkaline beef-broth culture days old. The thickest 

 rods observed on slides made from this culture and stained in a 

 saturated water}^ solution of basic fuchsin were 0.(] //. Most of them 

 measured 0.4 by 1.0 to 2.0/^. On slides made the third day from a 

 well clouded 1,000-cc. flask of distilled water containing 20 cc, of beef 

 broth, and stained with Dr. V. A. Moore's modification of Loeffler's 

 flagella stain, they were 0.5 to 0.7 by 1.0 to 2.0 /<. On slides made 

 from slant agar cultures 5 days old (stock 207, acidity -|- 22 of Fuller's 

 scale), and stained with Alfred Fischer's flagella stain, the largest 

 rods were 0.8 to 1.0 by 2.0 to 8.0 //. Some of these flagella-bearing 

 rods are shown in Plate I, figs. Oa and !»6. Flagella stains seemed to 

 slightly increase the thickness of the rods or to render visible an 

 outer part not stained by ordinary methods. In general the elements 

 of this species appeared to me slenderer than those of Ps. campestris. 

 Under the same conditions Ps. phaseoli is also a little plumper and 



