DISEASES, ETC. 63 



appear upon the surface in the form of white mould. The hyphos 

 is enabled to pierce the epidermis from the inside by the action 

 of a solvent substance excreted by the growing tip of the hyph< y 

 the protoplasm secreting a ferment which passes out and enables 

 the tip to corrode and dissolve away the substance of the cell- 

 walls. When the hyphoe- has protruded from the surface conidia, 

 or sporangia are developed, and these sporangia again give rise 

 to swarm cells, which have the power of movement in a drop of 

 water. " When a conidium germinates in a drop of dew or rain, 

 the normal process is as follows : The protoplasm in the interior 

 of the pear-shaped conidium becomes divided up into about 

 twenty or thirty little rounded masses, each of which is capable 

 of very rapid swimming movements, then the apex of the 

 conidium bursts and let these motile zoospores, a^ they are 

 called, escape." (Marshall Ward, p. 280). 



Each zoospor?. then swims about for a time and at length 

 comes to rest, commences to grow in about half-an-hour, and 

 then begins to bore its way again into its host. 



" The whole process of germination and the entrance / of the 

 fungus into the tissues, up to the time when it, in turn, puts out 

 its spore-bearing hyplue again, only occupies four days during the 

 moist warm weather in May, June and July." (Marshall Ward). 



It is probable, therefore, that under the conditions of heat 

 and moisture, which exist in Trinidad, the organism will have 

 still more rapid growth than in a temperate climate. The 

 average size of a conidium, according to the above author, is 

 l-400th of an inch long by 1 -700th of an. inch broad, and the 

 zoospores have a diameter of about l-200th of an inch, 



Having such measurements it is easily seen that a single 

 drop of water gives them as much room for movement, compara- 

 tively speaking, as a minnow would have in a mill pond. When 

 the fungus filaments, mycelium or hyphce., have become fully 

 developed, many branches begin to form an oospore or egg-like 

 spore. This spore is formed in a swelling of the free end of a 

 branch of the liyplioe, and contiguous to it is formed a differen- 

 tiated branch of the same hyphoe,, known as an antheridium, and 

 between these two organs, fertilization takes place. It has been 

 noted that some 700,000 oospores may be found on a surface of 

 less than a square inch. The oospores reach the ground in the 

 decomposing part of plants, and it is this fact which has caused 

 us to recommend the. entire destruction of all decaying material 

 in so strong a manner, from the time the subject was first dis- 



