ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
619 
Orchidese. They are characterised by the emission, when wounded, of an 
abundant pseudo-latex, white in V. Phalsenopsis , colourless in V. aphylla 
and planifolia. 
0 . Physiology. 
(1) Reproduction and Embryology. 
Embryology of Rumex.* — Mr. B. Fink has studied this in two 
American species, R. verticillatus and salicifolius. The development of 
the megaspore corresponds to that in Polygonum. The archespore divides 
first into a tapete and sporogenous cell ; the latter giving rise to four 
potential megaspores, one of which only is fertile, absorbing the other 
three. The development of the embryo-sac, the mode of impregnation, 
and the development of the embryo, present no special features. The 
definite (vegetative) nucleus does not divide till after impregnation. 
Embryo-sac of Scilla and Lilium.t — Mr. R. E. B. McKenney has 
followed out the development of the embryo-sac in species of Scilla and 
Lilium. In the anaphase stage of the original division of the archespore 
nucleus, the number of chromosomes which enter into the formation of 
the daughter-nuclei is eight. All the divisions of the surrounding 
nucellar cells, and the first division of the archespore, show 16 chro- 
mosomes. It is therefore probable that this last division of the arclie- 
spore is the reduction division. “ In the development of its ovule, Scilla 
may be said to differ from most plants in having a second macrospore 
undergo partial germination. In those species which develope more 
than one embryo-sac, each embryo-sac is developed as a rule from a 
separate archesporium. In Scilla the rudimentary second embryo-sac 
is developed from the same archesporium as the normal embryo-sac. 
Commonly it is the lowest cell of the chain of archesporial daughter- 
cells which becomes the embryo-sac. In Scilla , however, the lowest 
cell of the chain forms the second rudimentary embryo-sac, while the 
normal embryo-sac is developed from the cell above this.” 
Emhryogeny of the Balanophoraceae.* — Prof. R. Chodat and M. C. 
Bernard point out the different results arrived at by van Tieghem and 
Treub, and describe their own observations on Helosis brasiliensis. The 
structure described by van Tieghem as a placenta is regarded by them 
as an archesporial tissue. The archespore is remarkable from the size 
of its cells and the vigour of its nuclei ; the embryo-sac appears to 
develope indifferently from any one of its cells ; occasionally a second sac 
appears, more or less equivalent to the first. The primary nucleus 
divides into two ; the upper one alone developing normally, while the 
lower one becomes rapidly atrophied ; the former usually produces two 
synergids. The mother-cell of the endosperm is never the result of the 
fusion of two polar nuclei. At the moment when this nucleus divides, 
the egg-cell undergoes a change ; its nucleus loses almost completely 
its chromatophily ; from that time neither it nor the synergids can be 
detected; the endosperm finally completely fills up the embryo-sac. 
The embryo is very rudimentary, and appears to have originated from a 
cell of the endosperm. Directing spheres were observed, both in the 
* Minnesota Bot Studies (1899) pp. 137-53 (4 pis.). 
f Contrib. Bot. Lab. Univ. Pennsylvania, ii. (1898) pp. 80-6 (1 pi.). 
j Arch. Sci. Phys. et Nat. viii. (1899) pp. 92-4. Cf. this Journal, 1898, p. 555. 
