626 SUMMARY OF CURRENT RESEARCHES RELATING TO 
which is surrounded by the endosperm, by a long filiform appendage of 
the base of the sheath-like cotyledons. In the Cannacese it has a similar 
form ; the seed has no endosperm, and the absorbing organ is 
surrounded by the perisperm. In the Marantacem it is long and filiform, 
and hooked at the apex. In the Musaceas, e. g. Musa Ensete, it is 
broad and disk-like, resembling the scutellum of grasses. It remains in 
the seed, increasing greatly in size after germination. 
As to the morphological value of the absorbing organ, Herr 
Tschirch believes that the cotyledon takes a greater or less share in its 
formation, but that it does not in itself represent the cotyledon. It is 
remarkable that in seeds which contain no endosperm, a structure 
occurs with none of the functions of an absorbing organ, but which 
resembles it greatly from a morphological point of view. 
Anatomy of Cotyledons.* — According to Herr P. Kumm, leaf-like 
cotyledons exhibit a general agreement in structure with foliage-leaves, 
but are usually somewhat thicker ; the mechanical system is less 
strongly developed, and, except in lmpatiens , collenchymatous bundles 
replace the true bast-fibres. The simplest structure occurs in the 
cotyledons of exalbuminous seeds which remain permanently beneath 
the soil, as those of PJiaseolus and Vida. The palisade-parenchyme 
and epiderm are but feebly developed in the cotyledons of exalbuminous 
seeds. Stomates are found on all cotyledons which emerge above 
the surface, either on one side only or more commonly on both sides. 
Trichomic structures occur but rarely. 
Influence of Alpine situations on Leaves.f — According to observa- 
tions carried on by Herr K. Leist, the chief differences observed in the 
leaves of Alpine plants, as contrasted with those of lower altitudes, are 
in their diminished thickness and increased extent of surface. The 
former depends chiefly on a decreased development of the palisade- 
tissue. This may result either from the reduction of the number of 
layers of palisade-cells, or from a decrease in their vertical diameter 
and corresponding increase in their width, the number of layers remain- 
ing the same. The number and size of the intercellular spaces is 
increased ; the spongy parenchyme often becomes somewhat less close. 
The cuticle is considerably thickened. The causes of these peculiarities 
appear to be the lower temperature, and the excessive moisture of the 
ground at the time when the leaves are unfolding. 
Knees of Taxodium distichum.J — Mr. R. II. Lamborn describes the 
structure of the so-called “ knees” in Taxodium distichum , the deciduous 
cypress of the United States, roots w r hich project horizontally from the 
stem at a considerable distance from the ground, put out branches which 
descend vertically into the soil, and are frequently provided with knobs 
or protuberances on the upper side. He concludes that their function is 
not connected, as has been generally supposed, with the aeration of the 
tree, but that their purpose is to support it in the situations where it is 
* ‘ Zur Anat. einiger Keimblatter,’ 8vo, Breslau, 1889, 38 pp. See Bot. Centralbl., 
xlii. (1890) p. 163. 
f Mittheil. Naturf. Gesell. Bern, 1889. See Bot. Centralbl., xlii. (1890) p. 118, 
X Amer. Natural., xxiv. (1890) pp. 333-40 (1 pi. and 1 fig.). 
