SPORANGIAL TRICHOMES. 



By E. J. Duraxd. 



Several years ago while examining some sporangia of 

 Dryopteris thelypteris, my attention was attracted to cer- 

 tain trichomic outgrowths on the lateral walls near the 

 annulus. These took the form of rather stout glandular 

 or capitate hairs about equal in length to the diameter 

 of the sporangium. While some sporangia possessed 

 several hairs, others might be entirely free from them. 



The presence of tnchomes in such a position seemed 

 rather odd, so that the literature was examined to learn 

 whether the occurrence of such structures had been re- 

 corded. The only reference to anything at all compar- 

 able that I could find was the classical figure, reproduced 

 in nearly all the text-books, of the branch arising from 

 the stalk of the sporangium of Dryopteris Ulix-mas, and 

 which was regarded as a paraphysis, or perhaps an 

 aborted sporangium. The structure was, however, quite 

 different from the trichomes mentioned. About the same 

 time similar hairs were noticed on the sporangia of green- 

 house varieties of Hypolepis repens and Nephrolepis exal- 

 tata, which led me to believe that their presence was not 

 accidental, as I had previously suspected, but that they 

 might occur regularly in certain species. 



The interest thus aroused led me to examine herba- 

 rium specimens, in order to see how frequent the occur- 

 rence of such hairs might be. About two hundred species, 

 both native and exotic, were looked over. Of these, fif- 

 teen were found to possess sporangial trichomes. Eight 

 have only capitate hairs, viz. : Dryopteris thclypteris. 

 Poly podium crassifolium (Cuba). P. pectinatum (Cuba), 

 P. tenui folium (Cuba), P. taxifolium (Brazil), Phegop- 

 teris crinalis (Hawaii) . besides the greenhouse plants of 

 Hypolepis and Nephrolepis mentioned above. In every 

 case similar glandular hairs were also present on the sur- 

 face of the frond. Acute hairs occur in Phegopteris ap- 

 pend! attains (India), Polypodhtm heteromorphum 



20 



