44 FERTILIZATION 



numbering the carbon atoms); and (3), have OH groups in the 

 cis and not the trans position * on C^ and C^, if both C^ and C^ 

 have OH groups attached to them. This information suggests other 

 experiments to enable the perception mechanism to be examined 

 in greater detail. Some of the more obvious substances to try are 

 shown in Table 7. Compounds i and 2, Table 7, deal with the 



TABLE 7 

 Organic acids to be tried on spermatozoa o/Equisetum arvense 



question: does attraction occur if there are more than two OH 

 groups on C^ and C^; Compound i is in equilibrium with diketo- 

 succinic acid but the doubly hydrated form is believed to pre- 

 dominate : 



Compound 2 is equivalent to dihydroxyfumaric acid (which does 

 not attract bracken spermatozoa), because of the following 

 equilibria : 



Compound 3 deals with the question: is the configuration 

 HO-C-H necessary for attraction, given that the introduction of 



* The use of the words cis and trans is improper, but convenient, in this con- 

 text. Strictly, one should say 'have the meso configuration' instead of 'OH groups 

 in the cis . . . position'. 



