148 CYSTOPUS, OR WHITE RUST. 



between the parasitism of an Epiphyte Hke Erysiphe^ and that 

 of a highly speciaHsed ^cidiomycete Hke Piiccinia. I'here is not 

 only a difference between the mode of attacking or living upon 

 the substratum, but also as to the kinds and quantities of the 

 various matters absorbed. Thus, a Uredine in a leaf obtains 

 different food from a Claviceps in a grain of rye, or Ustilago in a 

 hypertrophied stem of Zea Mays; and that these differences may 

 be very important is fully demonstrated in cases of heteroecism. 



May it not then be possible that the sexuality of the higher 

 Fungi has disappeared because its purpose has been equally well, 

 or better attained otherwise than by means of sexual organs ? The 

 two points common to all cases of sexual reproduction are : — 



I. — A larger or smaller quantity of protoplasmic matter passes 

 from one portion (the male organ) of the same or another 

 individual, into the protoplasm contained in another portion 

 (the female organ). 



2. — The protoplasm contained in the female organ therefore 

 becomes capable of further development ; either at once, or more 

 generally after undergoing a period of rest. 



We have, in the germination and development of an oospore, 

 simply a renewal of the growth of the organism, and it seems 

 to imply — if the term may be allowed — a condition of weariness 

 on the part of the protoplasm. No doubt the molecular energy 

 of the protoplasm forming the oosphere is less than that of the 

 rest of the plant for the time being ; the access of the antherozoid, 

 or male protoplasm, however, reinvigorates the sluggish mass, and 

 renewed life ensues. This may require some time, however, and 

 we may possibly not be far wrong if we imagine that interval 

 to be occupied in molecular rearrangements in the mass. But 

 although we can sum up the foregoing by saying that after a 

 time, protoplasm requires reinvigorating by the addition of fresh 

 protoplasm from another source, it is extremely improbable that 

 the protoplasm of the male and female organs is at all similar. 



While we have reasons for believing that the mass of an 

 oosphere consists in the main of protoplasm such as occurs in 

 any cell capable of growth, it would be absurd to suppose that 

 the protoplasm of the male element is of the same nature ; on 

 the contrary, there is strong evidence that it differs extremely. 



