372 SUMMAEY OF CURRENT RESEARCHES RELATING TO 



part of the seedling to bury the stein apex deeply is continued by the 

 immature plants in the production of runners, which are more or less 

 comparable to the dropper of the seedling in structure. 



The persistence of the original stem apex until the establishment of 

 i Ik flower axis allows for the repetition of an indefinite scries of imma- 

 ture bulbs, formed from runners or in situ, but introducing no new 

 structures during the whole period of immature development. With 

 the formation of the flowering shoot, the vegetative structures become 

 secondary in importance, and the renewal bulb is developed from an 

 axillary, bred at the base of the shoot. The continuation of the indivi- 

 dual is thereafter without vegetative multiplication normally, the 

 increase being secured by the seeds. 



In the development of means of vegetative multiplication elongation 

 of the structure immediately about the stem apex (in seedlings the base 

 of the cotyledon, in the western forms the base of the petiole) was 

 followed by the elongation of the scales of axillary buds, thus forming 

 additional descending axes, each of which developed an additional bull) 

 from its terminal bud. 



The general development in the genus would confirm the assumption 

 that it is related to Tulipa, especially through T. sylvestris. 



Reproductive. 



Embryology in Euphorbiacese.* — J. Modilewski has made further 

 investigations concerning the development of the embryo-sac in Euphorbia 

 procera Bieb., in order to show its relationship with other species of 

 Euphorbia. This investigator finds that during the early stages of seed- 

 formation archesporial cells arise, which divide into suspensor cells and 

 embryo-sac mother-cells. All the mother-cells give rise to four nuclei, 

 but there is no subsequent cell-division. Only one of these mother-cells 

 ripens into an embryo-sac containing sixteen nuclei ; the remaining 

 mother-cells degenerate. 



In the other Euphorbiaceas there is only a single archesporial cell ; 

 the embryo-sac mother-cell divides into four daughter-cells, from the 

 lowest of which develops a typical embryo-sac containing eight nuclei. 



Gnetales as Apetalous Angiosperms.j — As a result of anatomical 

 research, 0. Lignier and A. Tison come to the following conclusions as 

 to the value of the flowers of Gnetales, and the systematic position of 

 the family. The type of flower is similar in the three genera — Welwit- 

 schia, Ephedra, and Gnetum — and in both sexes, and consists of an axis 

 rising from the axil of a bract, and bearing four verticils, of which two 

 may represent the perianth. The third forms the androecium with ter- 

 minal sori 1-, 2-, or 3-locular ; and the fourth, a closed ovary, with style 

 and stigma, containing an ovule reduced to the nucellus. The ovary is 

 basilar, and seems to be a continuation of the floral axis, but is very 

 probably foliar. The male flower of W. mirabilis is the only one in 

 which the four verticils are represented ; in other cases one at least is 



* Ber. Deutsch. Bot. Gesell., xxviii. (1910) pp. 413-18 (1 pi.). 

 t Comptes Rendus, clii. (1911) pp. 201-3. 



