iqiq] STEIL—PTERIS 473 



Apospory was induced in Pellaea flavens by growing prothallia in 

 continued darkness. When prothallia were transferred to sand 

 cultures there were produced some aposporous growths, but the 

 tendency to apospory was not pronounced. The aposporously 

 produced prothalHa in both species in turn produced apogamous 

 embryos and antheridia. Aposporous prothallia were also induced 

 as a result of regeneration experiments. When a portion of the 

 sinus of the prothalHum with a young embryo was removed and 

 maintained in culture, aposporous prothallia were occasionally 

 formed. When primary leaves were cut off and similarly placed 

 under cultural ct)nditions, prothallia were produced which devel- 

 oped antheridia but no apogamous embryos. 



Materials and methods 



A large number of cultures of Pteris sulcata L. were made during 

 the past 3 years by sowing the spores on steriUzed sphagnum 

 saturated with a one-tenth of i per cent Knop's solution or Beyer- 

 inck's solution as modified by Moore (17). The spores for the 

 cultural work were obtained from Dr. A. B. Stout, Bronx Botanical 

 Garden, New York, and Dr. E. B. Copeland, Los Banos, Philippine 

 Islands. An abundant supply of spores was also obtained from a 

 plant grown in the university greenhouse. 



In one of the cultures made March i, 191 6, the aposporous 

 developments to be described in this paper appeared. Many 

 young apogamously produced sporophytes were found in the 

 culture and on January i, 191 7, some of the young embryos pre- 

 sented a somewhat unusual appearance. As a result of microscop- 

 ical examination it was discovered that prothalloid portions were 

 present in certain parts of the sporophytes. In June 1917 a number 

 of aposporously developed prothallia were found to be present. 

 When some of the prothallia produced by the germination of the 

 spores were transferred to a new culture, made in a similar manner 

 to that of the original one, more aposporous developments were 

 produced. 



The prothallia and embryos from which the drawings and photo- 

 graphs were made were fixed in chrom-acetic acid solution diluted 

 with 5 parts of water, stained with Haidenhain's iron haematoxylin, 



