252 



HAItDWICKE'S SCIENCE-GOSSIP. 



spores and zoospores 

 are termed asexual, 

 because they are with- 

 out sex, as distin- 

 guished from other 

 bodies called oospores, 

 which are produced by 

 the contact of two 

 sexual spore - like 

 bodies, known as. the 

 antheridium, which is 

 the male, and analogous 

 with the anther, h, and 

 the oogonium, the 

 female, and analogous 

 with the ovary of a 

 flower, j. The oospores, 

 not till now seen for 

 certain in the potato 

 disease, are the true 

 resting spores. In- 

 stead of being transpa- 

 rent and unenduring, 

 as are the simple and 

 zoospores, these bodies 

 are at length dense in 

 substance, black- brown 

 in colour, and covered 

 externally with reticu- 

 lations or warts. They 

 are produced from the 

 mycelium, by the con- 

 tact of the antheridium 

 and oogonium in the 

 substance of the decay- 

 ing plant ; they are 

 washed into the earth, 

 and there they rest till 

 a certain set of condi- 

 tions makes them ger- 

 minate in the year 

 following their produc- 

 tion, just as a seed falls 

 and rests in the autumn 

 and starts again into 

 life during the follow- 

 ing spring. 



The terms here used 

 will be better under- 

 stood if the following 

 note is borne in mind : 

 The oogonium is analo- 

 gous with a pod, the 

 oosphere within an- 

 swers to the ovule, and 



the oospore (or resting spore) is the matured seed. 

 The antheridium with its contents is analogous 

 with the anther and its pollen. 



In various other fungi nearly allied to the potato 



V.'CS.AD.NAT.SC 

 Fig. 159. Transverse Section 



of a Fragment of Potato Leaf with Feronospora in/eeiang. 

 Enlarged 250 diameters. 



fungus these resting spores have been seen, mea- 

 sured, and illustrated, but till now the resting spore 

 of the potato fungus has eluded all search. The 

 reason generally given and accepted for its absence 



