310 M. C. COOKE ON CIRCUMNUTATION OF FUNGI. 



two. These tubes were hyaline and filled with very pale yellow 

 endochrome from the interior of the spore, and were of uniform 

 diameter, as nearly as possible, throughout their entire length. As 

 a rule only one of these two twin tubes went on growing. When 

 the major tube attained a length equal to several times the 

 diameter of the spore from which it sprung, it took a series of 

 spiral turns from right to left, or vice versa. At this stage the 

 tube presented a uniform diameter from end to end, but very soon 

 the basal portion of it became enlarged and empty, and soon after- 

 wards, at a short distance from the spore, a septum appeared which 

 cut the empty base of the germ spore from the remainder. Before, 

 however, this septum made its appearance, the abortive germ tube 

 became quite empty, and the greater portion of the endochrome 

 contained within the spore itself was transferred to the growing 

 tube. The active tube continued making spiral turns upon itself 

 like a corkscrew. The actual number of turns varied, as did their 

 direction, whether from right to left, or left to right. Very often 

 too, the tube would turn two or three times in one direction, and 

 then reversing its movement, take a few turns in the opposite 

 direction. The diameter too of the helix was subject to consider- 

 able variation. The sides of the tube were parallel to each other, 

 and its diameter uniform. At the extreme end, which was blunt, 

 there now appeared numerous irregularities which were incipient 

 branches. Not infrequently the end of the tube trifurcated, in the 

 manner of a trident. Usually one only of the main branches of 

 the trident continued to grow, the others remained rudimentary. 

 From this point all semblance of regularity in the contour of the 

 tube was lost, and it gave off lateral branches somewhat after the 

 manner of a stag's horn. The extremity of the tube did not even 

 now lose its tendency to convolute, although this movement is 

 considerably diminished. It is obvious that the spiral movements 

 above described are of great importance to the fungus, as by them 

 the growing mycelial tube has the chance of catching on any irre- 

 gularity of the cuticle of the host plant greatly increased. This 

 catching power is enhanced too by the trident-like terminal extre- 

 mity with its irregular branched outline. Similar results to the 

 above were obtained from watching the germination of the Uredo 

 of Coleosporium Tussilaginis, of Phragmidium ?nucronatu?n } of 

 Uromyces appendicidata and of SEcidium crasswn." 

 Knowing the readiness with which some of the moulds germinate 



