560 Black : The imbedded antheridium in Dryopteris 



grown in the greenhouse of the botanical laboratory of Indiana 

 University, were placed at my disposal, with the suggestion that a 

 study of the embryology be made with the view of ascertaining 

 whether apogamy existed or could be induced in this species. 

 Through the kindness of Mr, Alois Frey, a number of fruiting 

 fronds of ^^ Nephrodiinn inolle^^ w^ere obtained from the Lincoln 

 Park Gardens, Chicago, from which cultures were also made and 

 the prothallia studied in regard to the same problem. 



r 



Method of Culture 



Spores were sown upon sterilized soil in shallow earthen 

 saucers. These were then placed in larger saucers of about the 

 same depth. The cultures were watered with just enough dis- 

 tilled water after the spores had germinated to allow the prothallia 

 to grow slowly. Water poured into the outer dish soaked up very 

 slowly through the inner dish into the soil. This regulated the 

 rapidity in the absorption of w^ater by the soil and prevented the 

 cultures from being alternately dry and moist. Evenness of 

 moisture in the soil was further effected by placing a bell jar upon 

 small blocks of wood, about one inch and a half high, above each 

 -culture. This allowed free circulation of air around the culture. 

 This method prevented the collecting of moisture upon the dome 

 of the bell jar and falling upon the culture, thereby making fertiliz- 

 ation possible. The bell jars further protected the cultures from 

 -spores of fungi, etc. The prothallia grown under such conditions 

 ■grew slowly but thrivingly, A glance at a culture presented the 

 picture of a deep green carpet ; closer inspection revealed the 

 prothallia to be large, much larger than those, on which, under 

 normal culture, embryos appear. No sporophytes occurred on the 

 prothallia grown under these conditions. Material was fixed 

 from time to time in chrom-osmic acetic and chrom-acetic acids. 

 Prothallia were washed, dehydrated, and imbedded in paraffin. 

 Sections were cut 5 and 6 microns in thickness and stained in 

 safranin, Bismarck brown, and gentian violet. A detailed account 

 of observations on each fern will now be given. 



I. Dryopteris stipularis (Willd.) Maxon 

 Upon examining the sections, the prothallia were found to be 

 unusually large. The archegonial cushion presented, in most 



