398 Boodle . — Anatomy of the Schizaeaceae. 
the pericyclic cell. Sieve-plates in section in the longitudinal 
walls of the sieve-tubes may be best seen when the walls are 
slightly swelled with Schulze’s solution, as in the case of 
Fig. 47. After long-continued immersion in this reagent 
the walls become too much swelled and indistinct. Sieve- 
plates in section are not well seen in preparations stained 
with haematoxylene and mounted in canada-balsam, because 
the walls then become comparatively thin through dehydra- 
tion, £.s is seen in Fig. 48. The sieve-tubes are elongated 
elements with very long inclined end-walls (Fig. 48, e.). 
The conclusion to be derived from additional observations 
made since the publication of the first part of this paper is 
that the sieve-tubes of the Hymenophyllaceae agree in struc- 
ture with those of other Ferns. 
In examining the sieve-tubes the question of the perforation 
of the sieve-plates 1 was not attacked, but the observations on 
callus may be compared with some of the previous investiga- 
tions on the sieve-tubes of Ferns. 
De Bary ( 77 , p. 181) stated that the sieve-plates were not 
callous, and that he had seen the granules of contiguous sieve- 
tubes connected by thin filamentous processes which traverse 
the transverse pores in longitudinal sections of Pteris aquilina. 
Janczewski (’ 82 , p. 89) describes callus blocking the pores of 
the sieve-plate in Pteris aquilina , but regards it as quite 
exceptional for the Vascular Cryptogams. Russow (’ 82 , p. 
208) states that he has met with callus generally in the 
Vascular Cryptogams, but only traces of it in the Marattiaceae 
and Ophioglosseae. He mentions that the callus often takes 
the form of little rods traversing the membrane of the sieve- 
plate, and that there are usually small brilliant granules at 
the extremities of the callus-rods. In Pteris aquilina Terletzki 
(’ 84 , p. 487) describes refractive granules as aggregated on the 
pores of the sieve- plates, and quoting De Bary’s statement 
with regard to the filamentous connexions between the re- 
fractive granules, remarks that the granules are not connected, 
1 Poirault (’ 93 , p. 139) finds the sieve-plates perforated in Ophioglosseae and 
Marattiaceae. 
