54 RESEARCHES ON FUNGI 



the basal swelling or basal reservoir of the fruit-body and, owing to 

 its mode of origin, it is usually much elongated (under natural 

 conditions on horse dung 1-2 mm. long). It is on account of the 

 unusual length of the basal swelhng that P. longipes has received its 

 specific name. As the coarse hypha grows into the air, most of the 

 protoplasmic contents of the basal swelhng flow into it, and a thick 

 mass of red protoplasm always accumulates at the growing point 

 (Fig. 21, F, G). As soon as the hypha has attained a length of 

 several millimetres (under natural conditions on horse dung often 

 2-3 cm.), it ceases to grow in length and develops a sporangium at 

 its apex, and thereafter it develops a subsporangial swelling. Thus 

 the order of formation of the four parts of the fruit-body is as follows : 

 basal swelhng, stipe, sporangium, and subsporangial swelling. 



A Colourless Sporangial Wall as an Abnormality in Pilobolus 

 longipes. — Some normal fruit-bodies of Pilobolus longipes, having 

 the usual long cylindrical foot, rounded spores, and black sporangial 

 wall, came up on horse dung spontaneously in the laboratory ; and 

 some of the sporangia, after they had landed on a sterilised glass 

 slide, were used to inoculate sterilised horse-dung balls contained in 

 a large crystallising dish. The dung consisted of fresh balls obtained 

 from a stable and it covered the base and filled up about half the 

 space in the dish. The dish, after the dung had been inoculated, 

 was closed by means of a well-fitting glass plate. About a week 

 after inoculation, fruit-bodies of P. longipes began to appear on the 

 dung. They had the characteristic cyhndrical foot and rounded 

 spores, but many of them, although by no means all, were otherwise 

 abnormal. The development of the abnormal fruit-bodies took place 

 so slowly that the sporangia were not ripe in the mornings and 

 many of them were not discharged. The subsporangial swelhngs 

 and sporangia were remarkably small — not much more and very 

 often less than one-half the usual size ; and many of the sporangia 

 never turned black and remained bright orange-yellow. The 

 persistent orange colour of the sporangia was due to the fact that the 

 sporangial wall had failed to develop any black pigment, so that it was 

 colourless, thus permitting the orange-yellow spores to show their 

 colour through it. Many of the orange-yellow sporangia were 

 discharged, so that they struck and stuck to the side of the dish 



