89 



rivers in England and Scotland in Blue Book, C. 2660 for 1880, I would refer all 

 who are desirous of making a more extended acquaintance with the Scientific 

 knowledge of the Saprolegnia Fungus. For the present, I will endeavour, by the 

 aid of the drawings, to epitomise the character of the disease in such a manner as 

 to render it intelligible to those who have never had the advantages of seeing it 

 either with the unaided eye, or under the microscope. 



A microscopical examination of a vertical section through a diseased patch 

 reveals, upon its exterior, a number of slender transparent tubular filaments, 

 growing oftentimes in a singularly regular manner, and terminating generally in 

 rounded, although sometimes in tapering, club shaped, or pyriform extremities. 

 These tubular filaments (hyphte) are the stems of the plant, which, if traced 

 downwards, are found to have their rootlets ramifying some horizontally in the 

 superficial, middle, and deep layers of the epidermis, others vertically downwards 

 penetrating the true skin, disorganising its structure, destroying its nutritive 

 material, laying open the small blood vessels in its substance, and causing its 

 ulceration and sloughing. These rootlets are the miicelium, and correspond to the 

 " spawn " of our Mushroom beds. 



Beyond the margin of the diseased patch, the skin appears normal in structure. 

 The ulceration and disorganization follows the Fungus growth, thus indicating 

 that the Fungus is the primary cause of the disease and not its consequence. The 

 Fungus must therefore be classed amongst the epizoic fungi : its life commencing 

 externally, aa is the case with that of the potato disease, vine disease, hop mildew, 

 &c., &c. The Fungus stems are seed vessels (sporangia, zoosporangia. Fig. I., II.) 

 enveloping a colourless granular protoplasm of minute spheroidal cells, (spores, 

 zoospores). The cells rapidly increase in size, and when mature are liberated in 

 an ovoid form as zoospores or living spores from the extremity of the filaments, 

 having attached to them a pair of cilia or tail-like appendages, which g^ve them 

 the power of motion, and which alighting beyond the circumference of the dis- 

 eased patch are prepared to extend the disease centrifugally. Should the zoospore 

 fail to attach itself to any substance capable of giving it nourishment, it speedily 

 dies. Each sporagium contains swarms of these zoospores. 



In some instances, the zoospores germinate within the zoosporangium itself, 

 as is seen in diagram Fig III. (dictyosporangium). 



There is yet another method of reproduction. The hyphae break up into 

 joints which are capable of germination. The short branch of a hypha dilates 

 into a spheroidal capsule with a thick cellular covering within which protoplasm 

 is developed, containing one or more spheroidal masses called oospores. This 

 capsule is called an oosporangium (Fig. V.) Fecundation probably takes place 

 where an antheridium from an adjacent branch of a hypha applies itself to the 

 outer wall of the oosporangium (Fig. V.), and the spores, when liberated from 

 their capsule, are enveloped in a thick tough skin, which enables them to re- 

 main quiescent, (as do the spores of the Peronospora infestans — the fungus of the 

 Potato disease — see Woolkope Transactions, 1875, p. 166) and for this reason are 

 called " resting spores." 



The well-known fact that the disease is propagated by these zoospores leads 



