76 ZYGOPHYCE.E. 



plete the process. The union of the two cells appears to take place in 

 several ways. In accordance with one plan, connecting tubes, pushed 

 out from near the ends of the cells, grow for a short distance nearly at 

 right angles to the long axis of the filaments, and then bend at a right 

 angle to themselves, so as to run parallel to the filament cells. The ends 

 of these processes are, of course, opposed to one another, and coming in 

 contact, fuse together so as to form a continuous tube for the passage of 

 the endochrome. Another method by which neighbouring cells are 

 sometimes connected is by the formation of coadjacent pouch-like en- 

 largements of the opposing ends, and a subsequent fusion of these 

 newly-formed enlargements by the absorption of the end wall between 

 them." 



" There is still another method of conjugation, the so-called genuflexu- 

 ous, in which, instead of a connecting tube being formed as the medium 

 of union, two cells of opposing filaments become sharply bent back- 

 wards, so that their central portions are strongly thrust forward as 

 obtuse points, which, coming in contact, adhere, and allow of a passage- 

 way between the cells being made by the absorption of their cohering 

 walls." Wood's F. Water A Ig OB, p. 161. 



Hassall says that the conjugation in Zygnwmacece results in the pro- 

 duction of " a dark body, of either an oval or circular form, and en- 

 veloped in membrane, which Vaucher, Decaisne, and Jenner regard as 

 the true spores, but which Agardh declares resolve themselves after a 

 time into zoospores, an opinion in which I concur, applying the term 

 sporangia to them." It need scarcely be added that this view is erro- 

 neous, the resulting body germinating direct after a period of rest, and 

 termed a zygospore. 



The same author makes also another statement, rather vaguely stated, 

 which is not confirmed by experience. " It is curious to remark that 

 the cells in one part of the same filament will part with their contents 

 and remain empty, while in another they will be the recipients of the 

 contents of the cells of another filament." His remarks on agamaa- 

 sporous Conjugates will be illustrated under the sub-family Gonatonemeos. 



Sub-Family 1. ZYGNEME^E. 



Cells cylindrical, united in threads. Zygospore undivided, 

 and mostly contracted, passing into the resting condition, after- 

 wards developing into a germ-cell, divided into a basal cell, and 

 a thread-cell, capable of division. 



As hereafter explained, this sub-family differs from the Mesocarpece 

 chiefly in the development of the spore, which is not surrounded, or 

 accompanied, by two to four deciduous lateral cells. 



GENUS 44. ZYGNEMA. Kutz. (1843.) 



Cells with two axile many-rayed chlorophyll bodies standing 

 near the central cell nucleus, each containing a starch-grannie, 

 or quite filled with dense granular contents, surrounding two 

 starch-granules lying near the centre, (a) 'zygospore in the 

 bladdery middle space between the ladder-like united pairing 

 cells (), copulation ladder-like, or lateral between two cells 

 of the same thread. 



