16 
of these branches, as well as the hardness and rigidity of these 
peculiar cells, together with their great number, we must assume that 
they serve as a mechanical contrivance to prevent the collapse of the 
wide air-passages which, without them, might take place on a sudden 
or gradual change in the radial pressure exerted on the plant by the 
water and the atmosphere. 
This summer I planted a cluster of the spur-like rootlets men- 
tioned above in some sand contained in a shallow dish and covered 
with a few inches of water. The bud above the rootlets soon sent 
up some of the submersed leaves, which, in shape and size, exactly 
resembled the ones collected from the actual habitat of the plant. 
But on closely examining their petioles I was surprised to find that 
they did not contain a single stellate cell! I do not venture to con- 
sider this single observation as a proof of the correctness of the above 
theory, but it certainly does not contradict it, and invites closer in- 
vestigation. 
Hoboken, December 1884. 
Explanation of Plate xlvhi. — Fig. i. Cross-section of filiform stem. .?, 
epidermis; se, sub-epickrmal layer of parenchyma consisting of two or three rows of 
cellsvvith few and small interstices; i, intercellular air-canals; ic, air-canal magni- 
fied in Fig. S; /, partitions between air-canals; cd, central fibro-vascular bundle; /^, 
lateral bundles; x 36. Fig. 2. The central fibro-vascular bundle of Fig. i, x 370. 
en, endoderans; v. ducts (annular and spiral): sv, sieve tissue. Fig. 3. Central 
fibro-vascular bundle of filiform petiole. Letters as in Fig. 2; x 370. Fig. 4- f^ 
few of the numerous stems, leaves, etc., of a full grown plant to illustrate its habit. 
The fiUform petioles and stems of the original were about .5"^- long. l>t, bottom of 
lake; si, submersed leaves, sc, scales; pf, filiform petioles; st, filiform stems; rp, 
spur-like roots; sf, surface of water. Fig. 5. Eases of leaf-organs. Letters as m 
Fig. 4. Fig. 6. Young plant that has grown from tlie spur-like roots, sp. Fig. 7- 
Cross-section of one of the spur-like rootlets (Fig. 4). e, epidermis; pc, narenchyma 
cells; en, endodermis; v, ducts; sv, sieve-tissue; x 36. Fig. 8. Iniercelhilar canal, 
ic. Fig. T, X 36. ^;^, stellate ** hairs"; other letters as in Fig. i. Fig. 9. Longitud- 
inal section through air-canal and stellate "hair"; x 370. Fig. lo, Longiladmal 
section through air-canal, giving front-view of stellate *' hair", the invisible half of 
which extends behind the partition into the contiguous air-passage; x 370. 
All the powers given refer to the original figures as drawn with the camera ; 
the plate they appear reduced to one- half their size. 
On the Mechanism of Anthesis in the Ericaceae 
By H. H. RusBY. 
As to the anthers, a strong distinction exists between the Pyjoh- 
nese and the remainder of the Ericacese, in that the pores are basal m 
the former, apical in the latter. But this characteristic is not so readuy 
made out as would at first appear. On examining a mature flower in 
any sub-order, the pores are found uppermost, and the only apparent 
indication of inversion in the Pyrolinese is the common extrorseness ot 
the pores, the anther itself being introrse. But even this distinction 
vanishes, nearly, in Clethra, where the poriferous horns are twisted so 
as to face laterally, and quite so in Clwnaphila, where the horns are 
in 
f 
very short, and the openings look obliquely upward and inward. >vne 
we turn to the bud of Clethra, we find the filament doubled upon itself 
so that the poriferous horns are pointing downward. In very yf ^"» 
buds this reduplication of the filament is not apparent, the fold 
