FERN GROWING 129 



pronounced one, of each character. If we suppose a slight trace 

 of any one character to be the result of impregnation by any 

 one sperm, then where the character is more pronounced it is 

 equally fair to assume that this is the result of a number of 

 sperms having that character, and that a varying number 

 of male sperms entering into each cell has been the cause 

 of the various differences. 



Taking a deduction of the evolution of sex, it may be stated 

 that the preponderance of the number of males over females 

 seems to hold good both in the animal and vegetable kingdoms. 

 The author has found the proportion of males to females in the 

 yew as 107 to 100, in the aucuba as 123 to 100, in calves as 1 16 

 to 100. Statistics show the excess of male over female children. 

 In making any deductions, this excess has to be accounted for. 

 It is only safe to take an average of a series of years, for the 

 numbers differ in different years. Amongst cattle the author 

 has known as many as ten males to one female, and vice versd; 

 also that some years produce many more twin calves than the 

 average ; this is well known with sheep. 



Having proved that an excess of male pollen from a pink- 

 flowered Dahlia when applied to a single white Dahlia will 

 produce an increase in the number of white seedlings (for we 

 may call the seed-bearer the female), the next step has been the 

 endeavour to find out the true cause of determination of sex. 

 An experiment has been made with a dioecious plant, i.e., having 

 unisexual flowers of the same species that are produced on 

 distinct individuals. In this experiment an excess of pollen 

 has been used in crossing an aucuba, but time will be required 

 to grow the seedlings to maturity. This experiment may 

 enable us to obtain proof as regards the evolution of sex from 

 experimental observation without the aid of the microscope. 



Nature assists in overcoming difficulties in various ways, 

 and throughout the vegetable kingdom we are familiar with the 

 help given to certain flowers by insects. 



