312 HOFMEISTER, ON 



rudiment is at this time almost hemispherical, without a 

 trace of a division. The fore-edge of the base of a frond is 

 not in organic connexion with the tissue of the end of 

 the stem upon which it rests ; at this place there is a low 

 but tolerably wide fissure (PL XLII, figs. 10*, 1 1). In the 

 second summer a flat cellular mass first makes its appear- 

 ance out of the rounded apex of the frond-rudiment : this 

 is the rudiment of the sterile frond, upon which the lowest 

 pinna?, of the lamina first make their appearance. Whilst 

 the next four, five, or six segments of the sterile frond are 

 making their appearance on the continually-elongating end 

 of the cellular bod}^ (and frequently also at an earlier period), 

 a button-shaped cellular protuberance becomes visible close 

 underneath, and almost between, the oldest pinna? of the 

 sterile frond ; this is the rudiment of the fertile frond (PL 

 XLII, fig. 2). So far the pair of fronds is developed up to 

 midsummer of the second year. The further development 

 remains dormant until the following spring. During this 

 time the transverse fissure which divides the fore edge of 

 the sheathing base of the frond from the underlying tissue 

 continues still open for a short space ; it forms a direct 

 communication between the hollow spaces which enclose 

 the pairs of fronds for the second and third following years 

 and the terminal bud. The transverse fissure first disap- 

 pears during the vegetative period in which all the parts 

 of the pair of fronds are completed, — twelve months be- 

 fore the final appearance above ground, — whilst the rami- 

 fications of the fertile frond proceed from the protuberance 

 in front of the points of insertion of the lowest segments of 

 the barren frond. The development, as in the barren frond 

 and in the fronds of ferns, is centrifugal.* 



Development of the vegetative organs of OjjJiioglossum 

 vulgatum. — The thick covering of cellular tissue which sur- 



* Roper has made an interesting observation ('Bot. Zeit.,' 1S59, p. 257), 

 viz., that plants of BotrycMum Lunaria growing in loose sandy ground sometimes 

 exhibit lateral ramifications on the subterranean stem, originating, it would 

 seem, from the formation of adventitious buds underneath the base of the frond. 

 The growth of these lateral branches resembles to a great extent that of germ- 

 plants, inasmuch as at first they form scaly leaves only, and ultimately, when a 

 leaf first appears above ground, fertile and barren segments are formed contem- 

 poraneously. 



