of the Fishery Board for Scotland. 



373 



first day or two ; but later, however, we find curious currents set up 

 spontaneously in the tubes and the granules begin thus to be congregated 

 in or near the blind extremity. Later, this terminal portion becomes 

 packed closely with the granular protoplasm, and then at some little 

 distance from the top a septum makes its appearance which shuts off a 

 quantity of the granular material from the rest of the tube, and in this 

 isolated terminal portion spore formation begins. 



The granular matter here accumlated now takes up a central position 

 with reference to the portion of the tube within which it is included, and 

 is surrounded by a regularly disposed layer of clear protoplasm, like that 

 which is found within the rest of the tube. Growth now manifests itself 

 in the central granular area ; so that, as a result of this, the shut-off portion 

 begins to swell and assume a somewhat pyriform aspect. By-and-by the 

 granular matter begins to undergo a process of division, so that rounded 

 masses are formed, and this progresses until this pyriform shut-off portion 

 is seen to be filled with round shot-like granular bodies, which react to 

 staining agents in the same way as does the granular material found 

 throughout the tube. This division of the protoplasm is not affected 

 simultaneously as certain observers have supposed, but is a gradual change, 

 first obtaining in the more central parts and then progressing outwards. 

 After the process just described has come to an end, the free end of the 

 closed sac ruptures and the enclosed spherical bodies escape. After the 

 case has become emptied of its contained spores, it does not drop off at 

 once as might be expected, but a new case is seen to push its way upward 

 and through it from the common tube behind. This peculiarity is character- 

 istic of the genus of fungi known to botanists as Saprolegniae. Before 

 proceeding further, however, a word or two may not be amiss by way of 

 properly defining the various structures which have just been described. 



The collection of long tubes of which the fungus mass is composed is 

 known as 'mycelium' and the individual tube units are known as 

 1 hyphse.' To each of the terminal portions, which have become shut off 

 and filled with spores, is applied the name of ' sporangium,' while the 

 contents are known as spores. It happens, however, that in some cases 

 these spores when they escape are endowed with the power of locomotion, 

 which is effected by means of long excessively delicate hair-like bodies 

 attached to them and termed cilia. When such is the case the spores are 

 called 'zoospores' and the case or sporangium enclosing them a 

 ' zoosporangium.' 



It may be noticed that the spores contained in the sporangium when 

 nearly ripe assume, as a result of mutual pressure, a somewhat hexagonal 

 appearance; but I have never seen them assume a spindle shape as has been 

 described by certain previous observers. After the spores are discharged 

 they sink to the bottom and begin to germinate. This process is seen to 

 consist in the extrusion from the spore of a young mycelial shoot or 

 hypha. In some cases two shoots appear, while in others the single 

 shoot may be seen to branch almost as soon as formed. As soon as 

 this has occurred, the spore by means of its young shoot, may bore 

 its way into any suitable soil within reach. In several cases in cultiva- 

 tions of this fungus I have seen the young hyphae penetrate the wall of 

 an unopened sporangium. 



As the result of the observations of numerous workers, of whom may 

 be mentioned Pringsheim,* Cornu,f De Bary,^ Brefeld,§ and others, — 



* 'Die Entwickelungs-geschiclite der Achyla prolifera,' Nova Acta, 1851, p. 397-480; 

 Jahr.f. Wiss. Bot., i. 1857, ii. 1860, ix. 1874. 

 t ' Monograph ie,' Ami. de Sci. Nat. Botan., 1872. 



t Be Bary and Woronin 'Unters iiber die Peronosporein und Saprolegnien,' 1881. 

 § Botanische Untersuchungen, Hft. iv. 1881. 



