ZOOLOOY AND BOTANY, MICROSCOPY, ETC. 
587 
Eoot-tubercles of Isopyrum.* — Mr. D. T. MacDougal describes the 
tuberous thickenings of the fibrous roots of Isojpijrum biternatum, an 
American plant belonging to the Eanunculaceae. The cells of the 
nodules contain neither starch, nor sugar in its ordinary forms, but 
numerous organisms of a bacterial nature. The author suggests that 
these enable the plant to assimilate the free nitrogen of the atmo- 
sphere. 
C4) Structure of Organs. 
Male Flowers of the Box.| — Dr. F. Cavara discusses the nature of 
the 4 ‘ central body ” in the male flowers of the box. From a careful ex- 
amination of its structure in Buxus semjpervirens and in some other 
species, he concludes that the view of the majority of botanists — that it 
is a rudimentary female organ — is incorrect. He agrees rather with 
Delpino’s interpretation that it is a nectary closely connected with the 
opening of the flowers, and with the pollination by means of Diptera 
and Apidae. It presents none of the structure of an abortive ovary ; 
its cells do not contain starch, but sugar. 
Anatomy of Petals.^ — Prof. Luise Muller publishes an exhaustive 
account of the structure of the corolla in a great variety of flowers, 
especially those belonging to the Eanunculaceae, Nymphaeaceae, and 
Eosaceae. 
With regard to the epiderm of petals, the most common form of cells 
is the cubical ; the lateral walls are very commonly wavy or ribbed, 
especially on the under side of the leaf ; and this is much more gene- 
rally the case with Dicotyledons than with Monocotyledons. It is by 
no means most usual for the epidermal cells to be swollen into papillae ; 
this is more common on the upper than on the under side of the petals. 
Normal stomates occur not unfrequently ; imperfect stomates much 
more commonly. With regard to the contents of the epidermal cells, 
the chromoplasts result from the metamorphosis of leucoplasts or chloro- 
plasts. The leucoplasts very commonly contain starch, and chloro- 
plasts are not uncommon. The origin of the various pigments of petals 
is discussed, especially the connection between a red colour and the 
presence of tannins. Tannin was almost invariably found, either in the 
open flower or in the bud, in the epiderm or in the connecting tissue 
which surrounds the vessels. The authoress believes that the vacuoles 
are formed spontaneously in the protoplasm, and that their wall is an 
organic structure formed from the protoplasm. The peculiar structure 
of the epiderm of petals is especially adapted, in the first place for the 
attraction of insects, and in the second place for the storing up of water 
and prevention of excessive transpiration. 
The mesophyll of petals is greatly reduced, and is usually destitute 
of a palisade-tissue. The mesophyll contains, as a rule, but a small 
quantity of chloroplasts, chromoplasts, and pigments, but often a large 
quantity of excreta, especially of essential oils. The bud often contains 
large quantities of starch or glucose, which is more or less completely 
* Minnesota Bot. Studies, 1891, pp. 39-42. 
t Malpighia, viii. (1894) pp. 27-40 (1 pi.). 
J Nova Acta K. Leop.-Oarol. Akad. Naturf., lix. (1893) pp. 1-356 (22 pis.). 
