TREES AND SHRUBS 



the work of reproduction through conidia as hefore. Resting spores are 

 produced within the tissues, and carry on the attack anew in the spring. 



A large and important group of endophytes is that known as the 

 Uredines, in which there are three distinct stages of development, each 

 of which may he considered as a fungoid disease. 



The first stage is known as the "cluster cups," or aecidium form, and 

 consists of clusters of little cups, partly imbedded in the substance of the 

 leaf or twig of the host-plant. The margin is usually white and fringed, 

 and the interior filled with orange subglobose spores, termed a?cidiospores. 

 A species, exceedingly common in spring, may be found on the under- 

 surface of the leaves of the Lesser Celandine or Figwort {Ranunculus ficaria). 

 Less frequently it occurs on other species of Ranunculus, and is known as 

 the Crowfoot Cluster-cups. The " cluster cups " form of parasitic fungus is 

 found on many trees and shrubs. 



The second stage is reached in the summer, when on the same leaves, 

 or others, there are developed small brownish pustules, which at length split 

 irregularly, exposing a mass of minute brownish spores, each borne on a 

 short thread. These powdery spores, known as uredospores, constitute the 

 " rusts " which attack many plants. 



The third stage consists of teleutospores. These are produced in pustules 



similar to those of the second stage, and may sometimes be found mixed 



with them. They are more or less elongated, being supported on hyaline 



threads, and divided across the middle into two cells. Each of these cells 



may give rise to a germ tube or promycelium, and the apical cell may also 



produce secondary spores by cell-division. These last are eligible for the 



production of mycelium which on entering a new host plant will commence 



the cycle again. ^Ecidiospores, uredospores, and teleutospores may or may 



not be all produced on the same plant, but there are many variations, and 



the cycle is not always complete. Mycologists are divided in opinion, and 



there is still much to be learned before many of these life-histories are fully 



understood. 



Having given this brief sketch of their various phases, we will turn our 



lxii 



