232 ARCHER, ON DESMIDIACEJS. 



first time described, the tubular extensions are produced 

 directly from au addition to the original cell-wall itself, and 

 with which they are in absolute continuation, and through 

 the apices of which the cell -contents of the frond are emitted 

 by its own direct conversion into zoospores, and which are 

 green and comparatively large, after the manner of Cladophora. 

 Pringsheim seems to see little difficulty in supposing it as easy 

 for the zoospores in Pythium, having arrived at the surface 

 of a suitable confervoid, to penetrate or absorb their way into 

 the cell, as it is for their tubular necks in a similar manner 

 eventually to protrude from within through the outer wall. 



I have, however, lately met with a parasitic growth 

 attacking Closterium lunula, and which I refer doubtfully to 

 Pythium (Pringsheim), and of which Fig. 5 is a drawing. 

 Pringsheim' s plant, met with by him in the conjugated joints 

 of a Spirogyra, he refers to the family Saprolegnieae. That 

 observer suggests that a ramification of this parasite may 

 exist in the interior, so that the numerous projecting utricles 

 may possibly be connected amongst themselves within the 

 remains of the cell-contents of the infested Spirogyra. 

 Therefore, he says that the bodies with elongated necks may 

 actually be the sporangia, each separated from the vegetative 

 part of the plant by a septum placed deeply beneath the con- 

 tents of the infested Spirogyra-spore. This, however possible it 

 may be in Pringsheim's plant, does not seem to hold in the 

 curious growth figured (Fig. 5). Here, at least, each indivi- 

 dual plant seems to be a flask-shaped body, without any con- 

 nexion with its neighbours : in one case, indeed, I noticed 

 two of the necks, before penetrating the boundary Avails, to 

 inosculate within the frond of the Closterium. In a word, 

 each flask-shaped body, so far as I can see, may be said here 

 to combine in itself both the vegetative, as well as the fructi- 

 fying portion ; the whole plant at maturity being, as it were, 

 converted into a sporangium. 



In the earliest condition in which I saw tins plant, the 

 bodies within the Closterium appeared rounded vesicles, each 

 with a short neck. The neck of each, by gradual extension, 

 reaches the old cell-wall of the Closterium, penetrating which, 

 it grows to a very considerable extent into the surrounding 

 water. Just within the boundary wall of the Closterium, 

 each shows a very decided globular enlargement of the neck. 

 So far it appears to agree with Fringsheim'a Pythium. But 

 it differs therefrom, inasmuch as the cell-contents are green, 

 not colourless, as well as in the great length of the necks and 

 inthcext remit ics, w liilccaeh plant is filled with itscndnclirome, 

 being distinctly clavate. 



