PUCCINIA GRAMINIS 507 



and is travelling away from its sterigma, whilst at d is shown a 

 drop of the maximum size observed, just prior to the discharge of 

 itself and the spore contained within it. Some spores which ex- 

 creted large drops of the kind just described were never shot away 

 at all. Other spores, developed from submerged basidia, did not 

 excrete drops at all and were not discharged. Several such spores 

 were seen to germinate in situ, as shown in Fig. 203 at h, i, j, k, 

 and I (p. 503). At A a spore on the top of its sterigma has developed 

 an unbranched germ-tube : at i another spore has developed a 

 branched germ-tube. The spore, j, germinated as shown at k, and 

 then its germ-tube developed another spore which subsequently 

 germinated as shown at I. The germination of certain spores in 

 situ and the failure of some spores which have or have not excreted 

 drops to be discharged are doubtless pathological phenomena. I 

 consider that the excretion of the relatively enormous drops from 

 submerged basidia in the manner just described is also pathological. 

 It is to be doubted whether such conditions occur in nature as in 

 my artificial preparations. Moreover, excessive excretion of water- 

 drops is certainly a pathological phenomenon in a number of species 

 of Hymenomycetes. We have already seen that a large drop of 

 water was precociously excreted by a very immature spore of 

 Lepiota cepaestipes (Vol. II, Fig. 9, p. 19) and that an excessive 

 excretion of water sometimes takes place from the spores of Coprinus 

 sterquilinus and Psalliota campestris at the time when the spores 

 should be discharged.^ For the sake of comparison with Puccinia 

 graminis, the excessive excretion of water-drops by Coprinus 

 sterquilinus and Psalliota campestris will now be described. In 

 Coprinus sterquilinus, the normal size of the water-drop at the moment 

 of discharge is that shown in Fig. 205, B, at the base of the right- 

 hand spore. Occasionally, in some fruit-bodies which, perhaps, have 

 been observed or have grown under unusually moist conditions, 

 the drops continue growing and step up on to the body of the 

 spores in the manner shown for the left-hand spore of B. The drop 

 may then continue growing as shown at C ; and, finally, the spore 

 with its abnormally large drop may be discharged as is indicated 

 at C by means of the arrow. When the hymenium of a living gill 



1 Cf. vol. ii, 1922, pp. 17-18, 309. 



