68 VAN TIEGUEM AND LE MONNIER. 



the first may produce simple lateral branches with a large spo- 

 rangium ; the second may also give rise to new lateral branches, 

 but these are dichotomous and bear small sporangia. 



Thus, in pan cultivation we may meet with one or other 

 of the two forms of sporangia, either exclusively or both 

 together in diiferent regions of the mycelium, and the spore- 

 bearing systems will be accordingly either homogeneous or 

 heterogeneous. When both kinds of sporangia occur on the 

 same hypha sometimes the large sporangium is borne on the 

 summit, and the small sporangia laterally; and this is the 

 most common combination, but sometimes it is the reverse. 

 The hypha terminated by a tuft of small sporangia bears 

 a lateral branch with a large sporangium. The two arrange- 

 ments may even occur successively in the same complex 

 system; an erect hypha with a large sporangium bears a 

 horizontal branch terminated by a dichotomous tuft; this 

 produces in its turn an oblique lateral branch terminated by 

 a large sporangium, which in its turn produces a lateral 

 branch with small sporangia (fig. 18, i). 



The two forms of sporangium are always sharply dis- 

 tinguishable. The large sporangium is always borne by a 

 simple hypha, and has a large columella, a wall incrusted 

 with granules and fine s])icules of calcium oxalate which 

 becomes difiluent in water, dispersing the granules and 

 spicules and a large number of spores which in this way are 

 disseminated. The small sporangia are always produced by 

 dichotomous hyphae. Their short and very fragile pedicels 

 are separated from their cavity by a partition, which is flat 

 or only slightly curved ; their wall is also studded with more 

 or less prominent granules of calcium oxalate, but is not 

 soluble in water ; their spores are usually four in number, 

 but may be as many as six, eight, or ten, or as few as three 

 or two, or even be reduced to one filling the whole spo- 

 rangium. It is by the falling ofi'of these sporangia and the 

 final rupture of the membrane that the spores are set free. 

 Whether produced by a large or a small sporangium the 

 spores are in all other respects similar ; they are homogeneous, 

 colourless, or bluish, oval, about '008 to "010 mm. in length, 

 and '006 to "008 mm. in breadth. 



When the sporangium contains only a single spore, which 

 occasionally happens almost exclusively over a large extent 

 of the crop, the spore is spherical, intimately applied to the 

 membrane of the sporangium, from which it is distinguished 

 with difiiculty (fig. 20), but from which it can be freed by 

 pressure ; it measures often "012 mm. in diameter, but it may 

 vary from '008 mm. to '016 mm. It is probable that it is 



