280 H. MARSHALL WARD. 



empty membranes of the zoospores — and the name "Dictyu- 

 chus" was given to express the net-like structure thus pro- 

 duced. AVhether the genus "Dictyuchus^^ exists on a firmer 

 basis than this I do not know.^ 



With respect to the sexual reproductive organs of this 

 Achlya, my observations cover a considerable field; as before, 

 the description applies strictly to what I have seen. The 

 oogonia and antheridium branches become produced in 

 large quantities when the cultivated Achlya is allowed to re- 

 main quite still, floating on the surface of abundance of water ; 

 their presence is soon detected with a good hand lens, and 

 further examination gives the following information concerning 

 them. 



The oogonia arise as globular or nearly pear-shaped 

 swellings of the ends of very short branchlets, developed at 

 nearly equal intervals along the course of a vigorous branch 

 (fig. 9) ; the short branchlet is usually much smaller in dia- 

 meter than the parent twig, but resembles it in possessing thin 

 walls and coarsely granular protoplasmic contents, and in its 

 cylindrical shape. The balloon-like terminal swelling receives 

 a large supply of protoplasm, which accumulates in it as a yel- 

 lowish-grev dense mass, and then becomes shut off from the 

 pedicle by a thin, sharply-marked septum (fig. 10). In the 

 pedicle, which is about as long as the longer diameter of the 

 oogonium, the remaining protoplasm is much more Avatery 

 and poorer in granules ; the latter is inserted sharply, as it 

 Avere, into the parent branch, and there is no septum at the 

 base — the cavity of the two remains continuous throughout. 

 In vigorous specimens (fig. 10) the granules often seem to be 

 arranged in rows, embedded in the layer of transparent proto- 

 plasm lining the cylindrical cell walls. The groups of 

 Oogonia, marked by their yellowish-grey contents while 

 young, present a striking object (fig. 9), like groups of berries 

 developed in racemose order ; the pedicles are usually slightly 

 curved in various directions. As well shown in fig. 9, the 

 oogonium-bearing branches may be of various orders, very 



' De Bary, loc. cit., p. 94, says this abnormality occurs in other species. 



