ZYGOPHYTA. 127 
the nutritive medium, come near each otaer, and send out 
small branches, which come in contact with each other (a, 
Fig. 59); these elongate and become club-shaped, and at 
the same time they become more closely united to each 
other at their larger extremities (b); a little later a trans- 
verse partition forms in each at a little distance from their 
place of union (c); the wall separating the new terminal 
Hi 
oN gs 
Fie. 59.—Conjugation of a Black Mould. a. two hyphe near each other, and 
sending out short lateral tubes or branches, which come in contact; b, the 
branches grown larger; c, the formation of a partition near the end of each 
branch; d, absorption of the wall hetween the two branches. and the consequent 
union of the protoplasm of the end cells; e, resting spore fully formed. e mag- 
nified 90 times, the others nearly the same. 
cells is now absorbed, and their protoplasmic contents unite 
into one common mass (d); the last stage of the process is 
the secretion of a thick wall around the new mass, thus 
forming a zygospore (e). 
268. The resting spore does not germinate until it has 
undergone desiccation, and has experienced a certain period 
of rest, when, if placed in a moist atmosphere, it sends out 
hyphe which bear spore-cases. Resting spores appear never 
