orientation lu lh ) lUnaaliou of itc rayo.lt was at once very 



evident that for most spores the formal? provaiirs when the spores are 

 within a short distance of eachf other --- .2 mm. or often more --- 

 and beyond this distance, the chemical^) stimulus becomes too weak 

 and only the light is able to determine the polarity of the plant. 

 Only the comparatively isolated spores therefore ever show the orient- 

 ation to light ; i-rrj )i I'JL I'H-iml with the^ource^ of illumination uned 



here. 



The phenomenon is V3ry conspicuous ia groups o"' 2, 3, or 4 



eggs as well as in masses of fifty or a hundred.. In these 1 ,rge ,-roups 

 it is made evident by the invariable rtile that no ;%fl/^/rhizoid ever 



extends outwards from a group. Then two spores are within the distance 



which 

 through the stimulus is effective, the first cleavage planes of the two 



are often parallel and the rhizoids grow towards each other and often 

 meet tip to tip. The groups of five or six often make symmetrical 

 star-like designs when the rhizoids have grown and p/oject beyond the 

 group. 



""he spores are more rarely affected in thas way when the distano^ 

 between them is over*>.3 mm^but the phenomenon is sometimes observed 

 in spores as much as O.5 mm. apart. Tithin a distance ofo.2 mir.. 

 there are practically no exceptions. 



^he relative sensitiveness of a sj ore towards light and 

 towards this cherr.ical( ? ) stimulus varies greatly for different 

 spores. "'hen cultutes were placed in the window to get as strong 

 a light stimulus as possible in order to determine at what distance 

 from each other the eggs had to be not to show a greater sensitive- 

 ness towards/the chemical stimulus than towards the light, it was found 

 that^this distance followed no rule, the scores showing the greatest in- 

 dividual differences. Of two spores lying within 0.3 mm. of each other 

 one might be ^entirely oriented by the adjacent sporephile the otherj 

 apparently like it, Would show only the action of the light stimulus. 



