246 PRACTICAL BOTANY 



more convenient and successful to study the development and 

 structure of the zygospores in an allied form, in which they are 

 produced in profusion, viz. in Sporodinia grandis, Link. ( = 

 Syzygites megalocarpus, Ehr.). 



Sporodinia is a fungus which may frequently be found in 

 autumn, growing parasitically on many of the larger, fleshy 

 Hymenomycetes, especially on Russula, or Boletus : it appears 

 as a greyish or brown flocculent growth, and the zygospores are 

 of such a size that they can readily be seen as reddish-brown 

 bodies with the naked eye. While a part of the mycelium 

 ramifies in the tissue of the host, the zygospores are borne on 

 aerial branches : they may thus be easily recognized as brown 

 bodies, visible to the naked eye. 



Tease out a small piece of the flocculent mycelium gently in 

 water : examine under a low power, and observe 



1. The branched hyphee, which are light-coloured, and rarely 

 septate when young, but assume a brown colour, and form 

 numerous transverse septa at irregular intervals as they grow 

 old. 



2. The large brown zygospores, each supported by two 

 thicker, club-shaped hyphae (Syzygites form). 



3. The relatively small sporangia borne on branched gonidio- 

 phores, and having a structure similar to those of Mucor 

 (Sporodinia form). 



Compare a number of zygospores in various stages of deve- 

 lopment, and observe in them the following points 



1. The swelling of two neighbouring mycelial filaments 

 (suspensors), and their assumption of a position with their two 

 swollen ends opposite one another. 



2. The formation of transverse septa cutting off the apical 

 part of each suspensor, thus forming the two gametes. 



3. The two gametes in close contact with one another, while 

 the walls at the point of contact are gradually absorbed, the 

 absorption beginning at the central point : the two protoplasmic 

 bodies thus coalesce to form the zygote or zygospore. 



4. The increase in size of the zygospore, its contents becoming 

 dense and oily, while the wall at the period of maturity consists 

 of the following successive layers 



