176 



Fig. 93. 



Pi-lrocelis llfiineiiyi, liom the 

 Liiiifjfird (ZYi, sh(i\vin}» peculiiir 

 raiiiiticatioiis <<{ vertical lila- 

 nieiits. 390.1. 



hails are sometimes found given off from intercalary cells in the vertical filaments. 

 The cells producing them are usually more or less projecting, but the hairs are 

 feebly developed; they do not ordinarily reach the surface of the frond, and soon 



decay. Once only have I seen a few such hairs projecting 

 over the surface, as in fig. 94 E where the hair, however, 

 is terminal on a one-celled branchlet\ — The crusts may 

 certainly reach an age of more than one year, hi crusts 

 growing on stems of Laminaria hyperborea a stratification 

 is often visible which seems to be due to the cessation of 

 the growth in winter; in the part of the crust beneath the 

 limitating line empty or abortive fructifications may be 

 found, while new fructifications have not yet been produ- 

 ced in the upper part of the frond apparently formed after 

 the hibernal rest. 



Characteristic of the genus are the intercalary spor- 

 angia. In this species there are as a rule several consecutively in the same fila- 

 ment, in Danish specimens frequently six at least in a row, but there may be up 

 to nine. The row is never interrupted by sterile cells. The sporangia are situated 

 in the upper part of the vertical filaments, only the (1 — ) 2—5 uppermost cells 

 being sterile. The sporangiferous vertical filaments are usually unbranched, but 

 sometimes a branch is given olf, rarely from the articles transformed into sporangia, 

 more frequently from the cell subjacent to the sporangial series (fig. 95). The spor- 

 angia are first divided by an inclined transverse wall and then by two walls per- 

 pendicular to the wall first formed. The latter are frequently parallel, but the lines 

 of intersection with the transverse wall do not coincide. These seriate sporangia 



are of about the same height as breadth, 14 — 17 ju 

 broad, 16— 23 a high. 



hi most of the crusts only seriate sporangia 

 are present; but in some cases the sporangia were 

 single or at most two in a series. These sporangia 

 are more lengthened than the seriate ones. A transi- 

 tional case is shown in fig. 95 D, where the series 

 contains only two sporangia. But in fig. 95 G and 

 H single, terminal or subterminal sporangia are 

 represented, hi fig. 95 H the sporangium seems to 

 be terminal, but I cannot assert that there has not 

 been one or more sterile cells which may be de- 

 cayed or possibly removed by the preparation. 

 Similar sporangia were found in a thin crust with 

 the ends of the filaments truncate; fig. 96 shows 



Fig. 94. 



Petrocelis Ileniiediji. Vertical filaments with 

 hyaline hairs. A—C from Be{«trup Vig; in 

 C the hairs have been thrown oil', the 

 chroniatophore of the cells is visible. D~ E 

 from Helleba'k, E after a living plant with 

 a well ileveloped hair at the top of a uni- 

 cellular branchlet. A—D, 400 : 1 ; E, c. 200 : 1. 



' Comp. L. KoLDERUP RosENViNGE, Hyaline hairs (Biol. 

 Arbejder, tilegn. E. Warming, 1911, p, 206). 



