ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 725 



Reproductive. 



Relation of Megaspores to Embryo-sacs.* — J. M. Coulter con- 

 tributes a short account of the present state of knowledge of the 

 embryo-sac in relation to the megaspore. The author observes that 

 genesis of the ernbryo-sac begins with the division of the mother-cell, 

 and that the two first divisions cannot be omitted if fertilisation is to 

 be brought about ; by these divisions the formation of megaspore nuclei 

 is accomplished. Several exceptional cases are then discussed. In 

 Lilium the reduction-divisions are only followed by one other division, 

 thus reducing the customary five divisions to three. This condition is 

 more common in monocotyledons than in dicotyledons. In Cypripedium 

 also the five divisions are reduced to three, but while in Lilium four 

 megaspore nuclei are used, in Cypripedium only two are involved. 

 Peperomia is to be regarded as intermediate between ordinary Angio- 

 sperms and Lilium and Cypripedium, since without reduction there would 

 have been thirty-two nuclei in the embryo-sac. Insufficient details are 

 known at present to explain the irregularities in the Araceae. The only 

 case in which there is any evidence of free nuclear division is in the 

 Penceaceas, and even this' is doubtful. The author concludes that the 

 nuclear divisions from mother-cell to complete embryo-sac must be 

 studied before safe conclusions can be made. There is a tendency to 

 eliminate the divisions following the reduction-divisions, but among the 

 Sympetalae this tendency does not appear to exist, and it cannot even 

 be regarded as very general among Angiosperms. 



Monospermous Capsules.! — A. de Candolle has investigated a large 

 number of plants bearing monospermous capsules, and finds that they 

 may be roughly classified into two groups — (1) monospermous fruits 

 derived from uniovular ovaries ; (2) monospermous fruits resulting from 

 the abortion of one or more ovules. The author does not favour the 

 view that all monospermous fruits are derived from polyspermous fruits, 

 and he considers that the facts already known as to the biological signi- 

 ficance of such fruits are too incomplete to justify any hypotheses in 

 this direction. Dehiscence may be regarded as of importance with 

 respect to seed-dissemination, but no monospermous capsule has yet 

 been found having seeds with hairs or hooks, or other means for 

 insuring transport by animals or other agents. The author regards 

 monospermous capsules as among those indifferent peculiarities of which 

 a plant might be deprived without suffering any inconvenience. 



Physiology. 

 Irritability. 



Influence of Light on the Growth of Rhizopus nigricans. % — 

 L. Raybaud has grown specimens of this fungus on artificial media 

 under different coloured glasses, and records his first observations. 

 Under dark conditions the filaments grow in an upright direction ; 



* Bot. Gazette, xlv. (1908) pp. 361-6. 



t Ajch. Sci. Phys. Nat. Geneva, xxv. (1908) pp. 228-48. 



X C.R. Soc. Biol. Paris, lxiv. (1908) pp. 1172-4. 



