266 PROCEEDINGS OF THE AMERICAN ACADEMY. 



branched hypliae which start from the mycelium like stolons whose 

 branches intertwine and develop zygospores at the places of contact and 

 crossing. Here one hypha produces a perpendicular outgrowth which is 

 duplicated by the second at the point of contact with the first. The out- 

 growths are at first equal in size and have a diameter not greater than 

 that of the hypha which bears them. The gametes cut off are generally 

 unequal in size, one being as long as broad, the other only half as long, 

 and there is generally a marked difference in the size of the mature sus- 

 pensors, the larger corresponding to the smaller gamete. The zygo- 

 spores occur entirely separate or in great numbers close together, and 

 are often the only form of reproduction developed from the hyphae that 

 produce them. At times the same hyphae may bear single sporangio- 

 phores near the origin of the zygospores. 



By growing the two strains opposed in a van Tieghem cell on the 

 proper substratum, it is not difficult to confirm most of these observa- 

 tions of de Bary. In addition to the vigorous stolons which may function 

 as conjugative hyphae, more or less branched slender filaments arise from 

 the mycelia of both strains and may ultimately give rise to sporangia or 

 remain sterile. Where these, however, come in contact with similar 

 growths from the opposite strain, progametes are produced which by their 

 development push apart the fertile filaments. A stolon arising from a 

 node may form progametes if it comes in contact with a filament of the 

 opposite strain, and may later give rise to another node or produce 

 sporangia in close proximity with the zygospores. 



When certain (+) and ( — ) strains are contrasted the young zygospores 

 and the hyphae connected with them are more or less filled with globules 

 of yellow oily material which gives a striking color effect to the line 

 formed by the young zygospores, while between other (+) and (— ) 

 strains of this species on the same substratum the young zygospores are 

 colorless. The color when most marked may invade the sporangiophores, 

 and such a culture shows that the young sporangia where zygospores are 

 being formed are bright yellow in color, while those in other parts of the 

 culture are a pearly white at the same stage of development.- It has not 

 been determined whether the yellow sporangia are common to both 

 strains, but such a condition is prob.able, since where the color is pres- 

 ent the oily material may occur in the hyphae connected with both sus- 

 pensors. It will be remembered that the peculiar appearance of these 

 young sporangia on certain nutrients when the " Harvard strain " was 

 first found and when it subsequently reappeared, suggested the idea that 

 zygospore production, in this as well as in other species, might be a 



