1900] OBSERVATIONS ON LESSONIA 327 
not stop abruptly where the inner ring of cortical tissue abuts 
upon it, but occasional medullary filaments run out between the 
thicker walled and more compactly placed filaments of the cor- 
tex. Trumpet hyphz, abundantly represented in younger pith, 
are not so conspicuous in material of this age. The character- 
istic sieve-tubes of Nereocystis and Macrocystis, as described 
by Parker, Wille, Oliver, and others, have not been seen in 
Lessonia. The tissue immediately outside of the pith has in 
cross-section much the look of sclerenchyma. The cells in 
longitudinal section are not conspicuously armed, nor, as one 
looks at the cross-section under the microscope, do they seem 
to lie in radial rows. The inner ring on both sides of the pith 
principally composed of such cells as have been described. 
The transition to the next outer ring is more clearly marked in 
the gross structure than under the microscope, and at first I was 
much puzzled because the thin sections which showed the rings 
"ety conspicuously when held up to the light did not show them 
clearly when placed under an objective. The occasion for this 
seems to be that cells of the new growth are at first somewhat 
ne armed, and in places stand in rows extending in a radial 
direction and at the same level. The walls, except over the 
tads of the arms, are very thick. This has been shown both in 
diagram and in camera-lucida sections in figs. 8-76. Cross see 
tions taken through a region where the armed-cell tissue con- 
-_ Such radial rows at the same level will here and there cut 
“ight Or more cells in such a way that the whole row comes into 
ey looking somewhat like a medullary ray. Since eae 
. eae rows are not all cut through the central ese 
Res. ee will preserye its tee ae poe 
.. e ‘medullary rays, s0-Calle pees 
i te pith rays), come out as streaks of lighter app vies 
ee “ross section. As the new ring of growth grows older 
. “segs their arms and become more condensed in see 
oe : his shortening of the arms, together with a less a : | 
hae Giren makes the light streaks shorter, sag ees Ch 
Yindistinguishable from the structure around them 1 
