200 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
(4) Structure of Org-ans. 
Podostemacese.* * * § — In the third part of his monograph of this natural 
order, Prof. E. Warming describes eleven species, five of which are new. 
As regards the systematic position of the order, he regards it as most 
nearly allied to the SaxifragacesB, with its vegetative structure modified 
by the habit of growing on a rocky bottom in rapidly running water. 
One of the most marked vegetative peculiarities of the order is the 
dorsiventral structure of the young shoots in all the species. 
Morphology of the Lauracese.t — Herr C. Mez treats the morphology 
of this natural order from the following points : — Phyllotaxis, leaves, 
bud-scales, inflorescence, flowers, fruit. The dissemination of the fruits 
is effected largely by birds, rodents, and apes ; pollination chiefly by the 
agency of insects. 
Dichotypism.J — Dr. M. Kronfeld distinguishes three kinds of dicho- 
typism, viz. heteranthic, heterocarpic, and heterocormic, depending on 
variations in the development of the flower, the fruit, or the vegetative 
organs respectively. He further points out that, instead of regarding 
the characters of a hybrid as resulting from a combination of the 
characters of the parents, we should rather see in them an evidence of 
the polarity of the protoplasm in the germinal cell. 
Stamens of Solanaceae.§ — Prof. B. D. Halsted states that in the 
order SolanacesB there are three modes of the dehiscence of stamens ; but 
that there is one character which is common to them, and limited to the 
order, viz. the presence of a cone or “ columella ” in each anther-lobe. 
Development of Pollen. || — M. L. Mangin has paid special attention 
to the nature of the walls of pollen-grains and their transformations. 
After giving the details of numerous observations, the author states that 
at first the membrane of the pollen-grain is homogeneous, and is formed 
of pure pectic compounds ; soon this membrane differentiates towards 
the exterior, and is transformed into cutin ; and a little later, internally, 
and in one part of its thickness it is found to consist of cellulose. 
Two layers can then be distinguished, the intine and extine ; but these 
two layers must be considered as the progressive differentiation of a single 
membrane. The structure of the membrane of the pollen-grain presents 
a striking analogy to the external membrane of epidermal cells. The 
author obtained the best results with Lilium candidum^ Asparagus 
officinalis^ Geplialaria tartarica, and Geranium pratense. 
Development of the Pollen-grains in Rosa.l! — M. F. Crepin gives 
details of an examination of the pollen of numerous members of the 
genus Bosa. In order to observe pollen a low-power objective only is 
necessary ; when placed in water well-developed pollen-grains swell 
* ‘ Familieu Podostemacese,’ Af h. 3, Copenhagen, 1888 (French resume), 72 pp. 
and 12 pis. 
t Verhandl. Dot. Ver. Brandenburg, xxx. (1888) pp. 1-31. See Bot. Centralbh, 
xl. (1889) p. 362. 
X SB. K. K. Zool.-Bot. Gesell. Wien, xxxix. (1889) pp. 65-6. 
§ Bot. Gazette, xiv. (1889) p. 260. 
il Bull. Soc. Bot. France, xxxvi. (1889) pp. 386-93. Cf. this Journal, ante, p. 56. 
*jj Civ. Soc. Roy. Bot. Belgique, 1889, pp. 114-25. 
