1893.] MICROSCOPICAL JOURNAL. 191 



germinate till the following spring when a tube known as the 

 promycelium comes out of a thin place atthe apex of the spore. 

 This tube is branched and bears small lateral bodies known as 

 sporidia. These germinate, and when falling on the proper 

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



II. — White Rust of Beets. 



This fungus (Ci/stojmsblitii) produces white pustules on both 

 sides of the leaf (Plate I, fig. 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 up nourishment from the cells. The fungus threads col- 

 lect in certain places from which arise erect threads known as 

 conidiophores (Plate II, fig. 2c). From the end of this thread, 

 spores (Plate II, fig. 1 and 2) are cut off, sometimes five or six 

 are found in one chain, the outer being the oldest. The conid- 

 iophores and spores are found in large numbers just under- 

 neath the epidermis. When sufficient growth has taken place 

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

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

 series has a thick cell-wall 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 into eight 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 at the ends of 

 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 body 

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

 The antheridium enters through the wall of the oogonium and 

 the protoplasm passes into the oosphere. As a result of this 



