212 HOFMEISTER, OX 



Almost contemporaneously with the appearance of the 

 second frond, numerous cellular hairs are seen upon the 

 terminal bud of the stem, which have been previously 

 visible, although more sparingly, upon the first frond. 

 Having regard to their position and their centripetal deve- 

 lopment, they are undoubtedly analogous to the scales of 

 other ferns, which indeed also appear primarily elsewhere 

 under the form of simple rows of cells. * In Pteris 

 aqidlina, Biclsonia rubiginosa, and Balantium Karstenianum 

 they do not progress beyond this primary stage of develop- 

 ment. 



From the time of the formation of the second frond 

 until the commencement of that of the third, the longitu- 

 dinal growth of the axis increases considerably, as it does 

 with each successive frond during the entire life of the 

 plant, unless prevented by unfavorable influences. At 

 this time, if not (as is not unfrequently the case, PL XXIX, 

 tig. 1) even before the formation of the second frond, a 

 twisting of the stem takes place. If the young stem is 

 supposed to be horizontal, the hinder surface of the first 

 frond is turned downwards ; the rudimentary frond was 

 parallel to the surface of the prothallium.f By the torsion 

 of the axis the direction of the third frond, and sometimes 

 even of the second, is turned away from it to the extent of 

 00. Henceforth the fronds are inserted on the sides of 

 the creeping stein, the fraction \ representing as before 

 their mode of arrangement. The plane of involution of the 

 budding stem (that plane in which all the turns of the 

 incurved leafy surface lie, and which is perpendicular to 

 the leafy portion of the frond) is at first radial to the axis 

 of the latter. This plane, however, soon stands at right 



* I will return to this subject hereafter. Multicellular hairs with intercalary 

 cell-multiplication, even in the direction of the breadth and thickness, occurs 

 here and there even on the leaves of phsenogams {e.g. Begonia, and the calyx 

 and corolla of Hibiscus Trionum). My observations do not confirm Kunze's 

 opinion that the shoots at the base of the stipes of Hemitelia cupensis, which 

 resemble the fronds of Trichomanes, are transformed scales. The reasons 

 therefore which induced me to consider the scales as leaves, and the fronds 

 consequently as leafy branches, fall to the ground. The scales are only a kind 

 of hairy covering; certainly a very highly developed one, as they frequently 

 contain chlorophyll; for instance in Platy cerium. 



f It is self-evident that in speaking thus of the direction of the frond no 

 account is taken of the secondary curving upwards of the stipes to the light. 



