ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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Bonnier was able to determine tliat the increase in weight of the mistle- 
toe is less than the amount of carbon which it has obtained from the 
atmosphere ; in other words, that it gives up a portion of its assimilated 
substances to its host. 
Assimilation by Parasitic Plants containing Chlorophyll * — Prof. 
G. Bonnier shows in what manner the chlorophyll, which certain parasitic 
plants contain, can lessen or even annul their parasitism. The following 
are his conclusions : — (1) From a physiological point of view, parasitic 
plants containing chlorophyll present all intermediate stages between 
a plant which is totally dependent on its host, and a plant which 
profits only by the mineral substances taken up by the roots of the host. 
(2) In certain cases there is a reciprocal exchange of assimilated 
substances between host and parasite. (3) One cannot always deduce 
the anatomical structure of a plant from its physiological functions. 
Thus two plants in the same family, Melampyrum and Euphrasia, possess 
similar chlorophyllaceous tissues, but have a very different power of 
assimilation. Thesium humifusum and certain species of Pedicularis 
have leaves of a deep green, but their assimilation is much less intense 
than that of Melampyrum. 
Physiology of Seeds.| — Herr A. Tschirch gives a record of a series 
of observations on the nutritive process in the seed, chiefly in relation 
to tropical Monocotyledons. The following are the more important 
results. 
All seeds of Monocotyledons which have a tissue containing a store 
of food-material (endosperm or peri sperm) have an absorbing organ 
which remains in the seed during germination, and absorbs the nutrient 
tissue. This organ is, in the dormant seed, either scutellum-like 
(Graminese-type), or clubshaped, leaf-like or filiform (Zingiberacese- 
type), or short and of indefinite form, when it increases rapidly during 
germination, and forces its way into the endosperm (Palm-type). The 
epiderm of the absorbing organ is sometimes provided with papillae, 
sometimes not. The absorbing organ corresponds to a similar organ in 
Gnetacese and Cycadeae, and possibly to the “ foot ” of the embryo in 
Vascular Cryptogams, and to the “ foot ” of the capsule of mosses. In 
the families of Monocotyledons destitute of endosperm (Helobiae and 
Naiadem), the organ which forms a sheath round the plumule is certainly 
a cotyledon, while, on the other hand, in the second and third types, the 
absorbing organ and the cotyledonary sheath (pileole or coleoptile) 
together constitute the cotyledon, which therefore consists of a sheathing 
portion, at first enveloping the plumule, of an absorbing portion which 
remains in the seed, and of an elongated portion or neck which unites 
the two former. 
Even in the Gramineie-type, and in seeds with “ swollen hypocotyl,” 
the pileole is the cotyledon ; while the morphological interpretation of 
the scutellum and of the “ swollen hypocotyl ” is doubtful. The coty- 
ledon of Ituppia, Pothos, &c., the “ germinal tubercle ” of Orchideae, 
and the “ protocorm ” of Lycopodiacese, appear to be functionless absorb- 
ing organs. In some families of Monocotyledons, the seed is furnished 
* Comptes Rendus, cxiii. (1891) pp. 1074-6. 
f Ann. Jard. Bot. Buitenzorg, ix. (1891) pp. 143-83 (6 pis.). 
