238 INTRODUCTION TO THE STUDY OF FUNGI 



In this way a much-branched plant is formed, with hair-like 

 terminal branchlets, which connect with the larger main stems, 

 and through these with the body of the original spore ; the 

 latter has grown in the meantime into a large round or elon- 

 gated vesicle at the expense of the Euglenae, which have been 

 exhausted by the rhizoids. When it has reached a certain 

 size, varying according to the food which has been supplied to 

 it, it shows itself to be a sporangium. It grows out at one 

 spot into a bluntly and irregularly cylindrical thick tube with 

 a delicate membrane, into which the whole of the protoplasm 

 passes, and is at once divided into swarm-spores. This process 

 of development may be repeated for many generations, and 

 leads to an immense multiplication of individuals, if there is a 

 sufficient number of Euglenae within reach. When this has 

 taken place, the course of events changes. The young plants 

 remain for the most part small and become gametes, which 

 conjugate in pairs, each pair forming a zygospore, and these 

 behave as resting spores. Of the two conjugating gametes, the 

 one which is the supplying gamete has usually a round and 

 larger body, but shows no other apparent difference before con- 

 tact with the other, the receptive gamete. The latter usually 

 continues to be smaller, and often very small, and puts out 

 rhizoid branches, and if one of these encounters a supplying 

 gamete it applies its extremity to it as a conjugating tube, and 

 increases in thickness, while it ceases to grow in length. The 

 membrane between the conjugating tube and the supplying 

 gamete disappears at the point of attachment, and an open 

 communication between them being thus established, the whole 

 of the united protoplasm of both gametes passes into an en- 

 largement of the conjugation tube, close to the point of attach- 

 ment ; the swelling gradually expands into a spherical vesicle, 

 and, being delimited by a membrane after receiving the proto- 

 plasm, becomes a thick-walled zygospore. The outer wall 

 assumes a pale yellow colour, which is in some cases smooth, in 

 others spinulose. The whole process of forming a zygospore is 

 completed in from six to seven hours. This zygospore is a 

 resting spore, and germinates when its period of rest is over, 

 producing a zoosporangium like non-conjugating plants. 1 The 

 1 British Fungi — Phycomycetes, etc., by G. Massee, London, 1891. 



