Observations on the fern rust Hyalopsora Polypodii 
E. JT. BARTHOLOMEW 
(WITH THREE TEXT FIGURES) 
A study of this rust on Cystopteris fragilis (L.) Bernh. was 
undertaken in order if possible to bring together the somewhat 
widely varying statements of different writers with reference to its 
life history. 
Lindau* states that Hyalopsora Polypodii (Pers.) Magn. has 
teliospores and uredinia, but no aecia, and that the uredinia have 
no peridia. Grovet describes teliospores and uredinia but no aecia; 
the uredinia, with no peridium, containing yellow, sessile spores of 
two kinds, respectively thick- and thin-walled, both repeatedly 
found in the same sorus. In his artificial infection experiments, 
Dietelt found that the first uredinia contained only thin-walled 
spores; later, however, thick-walled spores also were found among 
- the thin-walled spores and in many of the uredinia formed still later, 
the majority of the spores were thick-walled. Arthur§ describes 
the two kinds of yellow spores, which for convenience he considers 
respectively aeciospores and urediniospores, as being in separate 
sori; the aecia, containing the thick-walled spores, being without a 
peridium, and the uredinia, containing the thin-walled spores, 
having only a very delicate peridium; both kinds of spores borne 
singly on pedicels. 
The observations recorded in the present paper were obtained 
in two ways; by a study of fresh material both in the field and in 
the greenhouse, and by that of fixed and sectioned material. In 
both field and greenhouse considerable difference was noted be- 
tween the appearances of the sori produced in cloudy weather and 
of those produced during a period of sunshine. Several times during 
the months of May and June there were periods of cloudy weather 
* Kryptogamenflora fiir Anfanger 2. Berlin. 1912. 
+ The British Rust Fungi 375. Cambridge. 1913. 
t Ueber einige Kulturversuche mit Hyalopsora Polypodii (Pers.) Magn. Ann. 
Mycol. 9: 530-533- I91I. 
No. Am. Flora 7: 112. 1907. 
195 
