ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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of the chambers thus formed elongate as cortical growth continues. 
The septa consist of hyphal chains not broken by the rift. Variation in 
the length of the chambers is due to the breaking of the sieve-tubes at 
the regions of greatest strain ; these regions would naturally occur at 
unequal distances apart. Specialized sieve- tube areas are developed at 
the extremities of the pith area; and they appear to prevent undue 
elongation and strain from tearing down the midrib ; and probably 
they serve also as conducting vessels in the broken pith. Normally the 
haptera arise at the edge of the lower portion of the flattish stipes, and 
those arising from the flattish sides remain small and simple. The 
sporangia and paraphyses develop as they do in Nereocystis. In the 
formation of sporophylls a ridge is first developed along each sharp 
edge of the flattened rachis. A portion of medullary tissue passes out 
into each ridge. Rifts form in the medullary region. The ridge 
becomes irregularly and more and more deeply lobed, until the leaf- like 
sporophylls, each enclosing a portion of medulla, are formed. A. G. 
Growth of the Fronds of Nereocystis Luetkeana. — Annie L. 
Fallis ( Puget Sound Marine Station Publications , 1915, I., 1-8, fig.). 
Experiments show that the plant will grow as well when loosened from 
its foothold on the rocks, unless washed ashore or otherwise unfavourably 
situated. The holdfast serves only to fix the plant, and neither it nor 
the stipes nor bulb are necessary for the growth of the fronds. If the 
fronds be cut into very small pieces, each piece will grow independently. 
The growing region is not situated at the transition place between 
lamina and stipes. The basal limit of considerable growth is at the 
beginning of the flattened expanded part of the frond. The terminal 
limit of the growing region is difficult to fix. Growth gradually 
decreases towards the tips of the fronds ; relatively little growth occurs 
beyond 2 ft. from the bulb in an ordinary July plant. A. G. 
Notes on the Growth of the Stipes of Nereocystis Luetkeana. 
— Sarah M. Sheldon ( Puget Sound Marine Station Publications , 1915, 
I., 15-8). The stipes grows about the same when loose as when 
attached. The greatest growth region of the stipes in fairly mature 
plants is 2 to 4 ft. below the laminae, the rate decreasing towards 
the ends. The rate of growth measured in July was about 1 in. per 
day. A cut stipes usually dies from decomposition, apparently due to 
the action of organisms at the cut surface or within the hollow. A. G. 
Gas Exchange in the Pneumatocyst of Nereocystis Luetkeana 
(Mertens) P. & R. — Sanford Myron Zeller and Abigail Neikirk 
[Puget Sound Marine Station Publications , 1915, 1., 25-30). Collections 
of the gases in the pneumatocysts were made by means of a special 
apparatus between 3 and 4 a.m. and 3 and 4 p.m. The average variation 
of carbonic acid from day to night is 2*21 p.c., and of oxygen is 
1*398 p.c. The quantity of these gases differs therefore from day to 
night. The maximum increase of oxygen takes place, as was to be 
expected, immediately after the time of maximum photosynthetic activity ; 
while the maximum increase of carbonic acid occurs during the night. 
The greater range in variation of the carbonip acid may be due to its 
