570 SUMMARY OF CURRENT RESEARCHES RELATING TO 



African plant, the leaves of which have febrifuge properties. They 

 find, as previously suggested by Engler, tbat the source of the dru» 

 is Combretum altum Oiuill. and Perrot (= C. micranthum Don). The 

 divergence of views held by systeniatists as to the nature of the 

 plant is explained by its polymorphism. It may be a liane almost de- 

 prived of leaves or a densely leaved bush. In anatomical character, 

 the absence of phloem islands in the wood, it agrees with Combretum 

 micranthum, but differs from C. gluiinosum in which this tissue occurs. 

 This is an important point, as Heckel, working with inadequate ma- 

 terial, has described the plant as a new species, C. Raimbaulti, allied 

 to C. glutinosum. 



Reproductive. 



Development of Hamamelis virginiana. * — D. N. Shoemaker de- 

 scribes the development of the flower, the course of pollination, and 

 the embryology in this species. He finds the floral development to bo 

 as described by Baillon, except that only in one instance were there two 

 ovules in a carpel. At the time of flowering the ovule is small and in- 

 complete, and the maerospore indifferentiated. The pollen-grains show 

 great resistance to low temperature. Fertilisation takes place about the 

 middle of May, that is, from £ to 7 months after pollination. The 

 mature embryo-sac is typical. The endosperm uses up all the nucellus 

 except the epidermal layer. The embryo has a suspensor, and at 

 maturity has used up about one-third of the endosperm, when it lies 

 straight in the axis of the seed. 



Development of the Embryo-sac in Piper and Heckeria.f — D. 

 S. Johnson has studied the development and germination of the mega- 

 spore in two species of each of the above genera. The megaspore is 

 directly derived from the lower half of a hypodermal cell, and the 

 whole course of development is like that of typical angiosperms. 



Embryology of Limnocharis4 — J- G. Hall has studied the embryo- 

 logy of the South American species, Limnocharis emarginata. He finds 

 that the development of the ovules closely follows that in Butomus um- 

 bellatus as described by Ward. They arise as emergences from the 

 walls of the carpels without definite placental arrangement. Except 

 in the history of the embryo-sac the subsequent development is of the 

 usual angiospermous type. The hypodermal cell which forms the arche- 

 sporium is very early distinguishable ; a tapetal cell is cut off from it 

 but has no wall and is pushed towards the apex of the sac where it 

 subsequently disappears. The remaining large cell becomes the embryo- 

 sac without further division. The subsequent history of the nuclear 

 changes differs considerably from the usual course. The megaspore 

 nucleus forms two daughter nuclei, one of which passes to the micro- 

 pylar end of the sac and forms the egg-apparatus and upper polar 

 nucleus, while the other goes to the antipodal end and remains un- 

 divided. The upper polar nucleus migrates towards the antipodal end 

 of the sac where it divides transversely. The lower daughter nucleus 

 remains in position, being cut off by a wall across the sac, and forming 



* Johns Hopkins Univ. Circulars, xxi. (1902) pp. 86-7. 



t Tom. cit., pp. 85-G. 



X Bot. Gaz., xxxiii. (1902) pp. 214-9 (1 pi.). 



