SUMMARY OF CURRENT RESEARCHES RELATING TO 195 



Reproductive. 



Reproductive Organs of Phyllocladus alpinus.* — N. J. Kildahl has 

 studied the morphology of the reproductive organs of Phyllocladus, and 

 finds that the ruicrosporophyll has two sporangia which shed the micro- 

 spores about November. There are two prothallial cells, of which only 

 one is usually persistent. The ripe microspore has usually four nuclei. 

 The ovulate cone bears two to eight ovules, each with two integuments, 

 one thick and fleshy and the other thin and leathery. The integuments 

 are free and have no vascular strands. Numerous pollen tubes pass 

 straight through the nucellus to the archegonia, and discharge their 

 entire contents into the egg-cells ; just before discharge the body-cell 

 divides into two equal male cells, only one of which is functional. A 

 heavy jacket-layer of multinucleate cells surrounds the archegonium ; 

 there are probably two neck-cells. The pro-embryo contains at least 

 eight free nuclei before the formation of cell-walls ; there is a long 

 suspensor. 



Embryo-sac of Peperomia.j — W.* H. Brown has examined the 

 embryo-sac of four species of Peperomia, and finds that a single 

 hypodermal cell cuts off a parietal cell and then forms the embryo-sac. 

 The nucleus of the latter undergoes heterotypic division and then goes 

 into synapsis ; then follows longitudinal splitting of a continuous 

 spirein, and the chromosomes are formed from loops in the spirem. 

 The chromosomes may undergo a second division through the 

 longitudinal split of the first division In the last division of the 

 embyro-sac nucleus, cell-walls are formed on the spindles which cut off 

 one of each of the eight pairs of nuclei, while those remaining free fuse 

 to form the endosperm nucleus. Six of the inclosed nuclei degenerate, 

 while the egg and a nucleus occupying the position of a synergid 

 persist. There are sixteen nuclei in the mature sac apparently derived 

 from four megaspores, but there is not sufficient evidence to justify 

 " the conception of four megaspores in an embryo-sac to all Angiosperms 

 in winch a row of megaspores is not formed," since some divisions may 

 be omitted or the order transposed. 



Embryology of the PodostemacesB.t — F. A. F. C. Went has in- 

 vestigated the development of the ovule, embryo-sac and egg in the 

 Podosteinacere. A complete series of development was obtained for 

 Oenone Imthurnii and Mourera fluviatilis, while other species were less 

 fully studied. Results show that the development differs widely from 

 that of the ordinary Angiosperm, but within the limits of the order is 

 very uniform. The chief points of difference are as follows :— The 

 inner integument develops after the outer one and never extends as 

 far as the top of the nucellus. By the stretching and disintegration of 

 certain cells in the lower part of the nucellus, a pseudo-embryo-sac is 

 formed. This phenomenon seems to prove the existence of causes 

 acting in the ovule, favouring the formation of a large cavity which 



* Bot. Gaz., xlvi. (3908) pp. 339-48 (3 pis.). 



t Tom. cit , pp. 445-60 (3 pis.). 



J Proc. Akad. Amsterdam, x. 2 (1908) pp. 824-32. 



