ZYGNEMACE.E. 101 



Mr. Archer has thus described the present plant : " Cells short, vary- 

 ing from nearly quadrate to three or four times longer than broad, 

 according to the interval of time elapsed since division ; the contents 

 bright herbaceous green, forming an axile compressed band (never sepa- 

 rate stellate chlorophyll bodies as in Zyynema) ; the conjugation taking 

 place by short wide processes, which, along with the shortness of the cells 

 or joints, gives the pair of conjugating filaments somewhat the appearance 

 of a perforated ribbon-like structure ; the total cell contents of each 

 pair of conjugating joints became massed together into an elliptic zygo- 

 spore within the inflated transverse tube ; the longer diameter of the 

 zygospore placed vertically to the length of the filaments ; the cavity 

 occupied thereby not shut off by any septum from the cavities of the 

 parent joints. It was evident that there was no septum separating the 

 zygospore from the cavities of the parent cells, but it lay freely in the 

 inflated transverse process, though frequently in contact with its walls 

 about the middle." 



Plate XL1. fi.g. 2. a, sterile cells X 400 ; b, fertile cells with zygo- 

 spores X 200. * 



Sub- Family 2. MBSOOARPEJI. 



Cells cylindrical, united in threads, with axile plates of 

 chlorophyll. Zygospore the shape of the mother-cells ; not 

 contracted, separating by three to five partitions into a central 

 firm-walled resting spore, and two or four lateral decaying 

 cells. 



The method of conjugation and spore-formation in the Mesocarpce was 

 not thoroughly understood until it was investigated and explained by 

 De Bary (" Conjugaten," 1858), who first recommended the separation 

 of the Mesocarpece from the Zygnemeas, and their recognition as separate 

 families. His exposition of the conjugation of the Alesocarpece is thus 

 summarised by Wittrock* in a memoir submitted to the Swedish Academy : 

 "Two cells grow together in the common manner by conjugation out- 

 growths, and a resorption of the double septum between the two conjuga- 

 ting cells takes place. By this a cruciated or H-shaped double cell is 

 formed, in which at first no other change takes place than that the canal 

 of conjugation is somewhat widened, and that the chlorophyll-coloured 

 part of the contents of the double cell moves into the canal of conjuga- 

 tion, and into the parts of the double cell nearest to the canal. This 

 cruciated or H-shaped cell, thus formed immediately by the conjugation, 

 De Bary regards as the zygospore of the Mesocarpece, and gives it the 

 character of being ' not contracted ' in contrast with the zygospore of 

 ZygnemecB and Desmidiece. This zygospore exists, however, only for a 

 very short time as such. The above-named moving of the chlorophylla- 

 ceous bodies (not of the whole protoplasmic mass) into the connecting 

 canal having been accomplished, the zygospore is divided by two or four 

 septa into three or five cells, of which one, the central one, is a hypno- 

 spore, rich in chlorophyllaceons protoplasm (and later in oil), whilst the 

 two or four lateral cells, containing no chlorophyllaceous protoplasm, are 

 sterile, and soon going to die. Thus the Mesocarpece have, according to 

 De Bary, spores of two kinds, namely (1), zygospores, which are formed 



* "On the Spore-formation of the Mesocarpese." By V. B. Wittrock. Stockholm, 

 18/8. 



