18U3.I MlCROSC'Oi'ICAJ. .lULKXAi.. IIU 



gerniiniite till the Inllowiiif^ spring when u tube known iis the 

 proniyceliinn comes out of a thin place at the apex of the spore. 

 This tube is branched and bears small lateral bodies known as 

 sporidia. These {"terminate, and vviien falling on the j)r()ppr 

 liost, i. e., "seed beet," produce the aecidium-stage. 



II. — W'lirrK lUsT OF Hkkts. 



This fungus (Cyxtopus blifii) produces white pustules on ]»otli 

 sides of the leaf (Plate I, lig. 4). The mycelium of the fun- 

 gus vegetates in the interior of the leaf occuring in the inter- 

 cellular spaces. These threads send out small haustoria which 

 take uj) nourishment from the cells. The fungus threads col- 

 lect in certain j)laces (rom which arise erect threads known as 

 conidiophores (Plate II, fig. 2c). Fron) the end oi'this thread, 

 spores (Plate II, fig. I and 2) are cut off, sometimes live or si.x 

 are found in one chain, the outer 1)eing the oldest. The conid- 

 iophores and spores are found in large numl)ers just under- 

 neath the epidermis. When suflicient growth has taken pl:ice 

 the epidermis or outer layer of cells of the leaf is broken and 

 the wliite powdery spores are exposed. The outer spore of the 

 series has a thick cell-w'all in many cases, and is said not to 

 germinate. Germination of the other spores consists in break- 

 ing up of the protoplasm of the spore intoeiglit parts which be- 

 come zoospores. On escaping from the spore these soon come 

 to rest when a thin cell-wall is formed. It then germinates and 

 enters the stomata. Another kind of spore is formed later in the 

 season known as the oospore. These are the resting or winter 

 spores. 



The sexual method of reproduction is as follows : The my- 

 celium or vegetative part of the fungus enlarges attheeadsof 

 the branches, soon a round cell is cut off', the protoplasm sep- 

 arates into two portions, the outer is used to build up the walls 

 of the spore while the center (oosphere) receives the fertilizing 

 material. The whole is called the oogonium. While the oogo- 

 nium is forming another branch is sent up from the same thre id 

 which produces the oogonium but below it or in some cases, 

 this arises from another branch. This bent or club-shaped ])ody 

 is called the antheridium. It is tlie male reproductive body. 

 The antlieridium enters through the wall of the oogonium and 

 the protoplasm passes into the oosphere. Asa result of this 



