n THE AMERICAN MONTHLY [Mar 



turn, produce other clusters of uredospores. The clusters 

 of uredospores are of a pale brown. Uredospores are 

 called summer-spores, their function being to enable the 

 fungus to extend its area of distribution. Produced in 

 enormous quantities, and very rapidly throughout the 

 summer, it is easy to understand the swiftness with which 

 the disease can, and does spread ; the only limit being 

 lack of supply of pea-plants for it to attack. 



"In the autumn, when the host-plant is waning, a 

 second form of spore is produced from the same my- 

 celium that produced the uredospores earlier in the sea- 

 son. This second form of spore is known as a teleuto- 

 spore, or winter spore, and differs from the uredospore 

 in requiring to remain in a latent condition before it can 

 germinate. The function of teleutospores is to tide the 

 fungus over that part of the season — its season of discon- 

 tent — when the host-plant is not present for it to prey 

 upon. After remaining in a resting-stage during the 

 winter, the teleutospores germinate in the spring, and 

 give origin to still smaller spores called sporidiola or 

 secondary spores. These exceedingly minute secondary 

 spores are, as usual, dispersed by wind, and those that 

 alight on the Euphorbia leaves germinate, enter the tis- 

 sues, and, in course of time, produce the ascidiospores. 

 The secondary spores produced by the teleutospores ger- 

 minate only on the Euphorbia and not on the pea,whereas 

 the secidiospores formed on the Euphorbia germinate 

 only on the pea. 



"To effect a cure for the disease, it is only necessary to 

 remove from the vicinity one of the two host-plants es- 

 sential to its existence." — Massee. 



The mycelium in the Euphorbia not only goes on 

 producing the secidia as long as the host lives but 

 by the use of suitable reagents, such as caustic potash, 

 can be seen penetrating almost every part of the plant, 

 descending mainly by its vessels. During the winter, 



