242 William J. Hodgetts. 
II. Observations on ZYGOGONIUM ERICEI'ORUM 
The conjugating Z. ericctorum 1 occured last July on the 
surface of damp peaty soil in Wyre Forest, about three miles 
from Bewdley, Worcestershire, and although the alga was common 
enough in the vegetative state—mainly as the green-coloured 
form, phycoporphyrin being generally feebly developed, a result 
probably of the alga being usually shaded from direct sunlight*— 
yet conjugating filaments were generally rare. Numerous samples 
were taken, but these proved to be mainly in the vegetative state, 
showing cytological characters typical of the species, the cell-wall 
being thick and lamellated, while many of the filaments showed not 
infrequently short lateral branches ; in others conjugating threads 
were present although somewhat rare. A diligent search, however f 
resulted in numerous examples being seen, and every stage in the 
process of conjugation was eventually observed and a number of 
permanent preparations secured. 
Conjugation is always scalariform. Two cells of adjacent 
filaments put out protuberances which meet, while their extremities 
become flattened against each other, and adhere, owing to the 
development of mucilage from the outermost layers of the cell-wall 
(Fig. 1, A). The actual protuberance is due to the local increased 
growth of the innermost, more refractive, layer of the thick cell- 
wall breaking through the less dense outer layers, the wall of the 
outgrowth becoming thickened as it grows by the deposition of 
newer internal layers of cellulose. So far the deeply constricted 
chloroplast in each cell, with its two conspicuous pyrenoids, has 
undergone no evident alteration, but very soon after the two 
protuberances meet the chloroplast of each cell becomes much 
contracted, sometimes even assuming a roughly spherical shape, 
while the pyrenoids become less conspicuous—although still to be 
made out by staining with iodine. As the chloroplast contracts it 
gradually passes into the protuberance, together with the greater 
part of the cytoplasm, and is there cut off from the body of the cell 
by a curved partition-wall (Fig. 1, A). 
• Each gamete is thus enclosed in a special cell or garnet- 
angium, the two being separated by a thick double wall. The 
main body of the conjugating cell is by no means empty, but 
contains a notable amount of granular colourless cytoplasm, and 
1 The identification of the alga was kindly confirmed by Prof. G. S. West. 
* It is probable that the purple pigment in the cell-sap acts as a protective 
screen against the ill-effects of strong sunlight—see Fritsch (4) and the 
literature there cited. 
