134 PRACTICAL BOTANY. 



found in the sori on the leaves, look for sori on the pedicels 

 of the youngest flowers of Radish ; section, and examine. 

 It is not always easy to obtain material for this and the 

 following observation. 



7. Stain thin sections of the diseased flowers of Radish 

 with Schultze's solution and examine for the organs of the 

 sexual reproduction. The nearly spherical oogonia and 

 antheridia take a deep red stain. The antheridia are 

 smaller than the oogonia. Draw a typical pair. Notice 

 the ova in the oogonia. Find also in mature oogonia the 

 oospores which result from the fertilization of the ova. 

 These oospores are the resting spores. Protected by the 

 greatly thickened tissues of the flowers, they lie dormant 

 through the winter. In the spring they are set free by 

 the decaying of the flowers, are scattered about by the 

 wind, and falling on favorable plants produce new crops 

 of Cystopus. 



It may in some cases be possible to see a fine tube con- 

 necting the antheridium with the oogonium. Were the 

 antheridium necessary in all cases for the fertilization of 

 the egg cell, the connecting tube would be seen in many 

 cases, but it is probably the fact that fertilization is in 

 most cases by parthenogenesis. 



References for Reading. Goebel's " Classification of Plants," pp. 

 92-96 ; Vines' " Text-Book of Botany," pp. 291-293 ; Cooke's " Intro- 

 duction to the Study of Fungi," pp. 230-232 ; Bessey's " Essentials of 

 Botany," pp. 139-143; Bennett and Murray's "Cryptogamic Botany," 

 pp. 323-332 ; Arthur, Barnes, and Coulter's " Plant Dissection," pp. 

 43-51; Bower's "Practical Botany," pp. 491-496; Strasburger and 

 Hillhouse's " Practical Botany," pp. 256 f-258 ; Carpenter's " The 

 Microscope," pp. 567, 568; Sachs' " Physiology of Plants," pp. 370-390. 



The Water Molds (Saprolegniece). These are sapro- 

 phytic or parasitic plants that grow on the bodies of fishes 

 in the water, and in the case of a few species in the living 

 tissues of animals. It is this plant that causes a disease 



