188 SUMMARY OF CUKKENT RESEARCHES RELATING TO 



mesarch bundle consisting of a protoxylem with a group of primary 

 metaxylem on its inner and outer side. This type occurs in the peduncle 

 of the cone in Stangeria and Bowenia, in the leaves of Cordaites and 

 modern cycads, and in the cotyledons of Gingko and Cephalotaxus. But 

 in the stems of modern cycads, and the still more recent Coniferae, it has 

 given place to the endarch type in which the inner centripetal group of 

 xylem has disappeared, so that the protoxylem now forms the most 

 internal portion of the bundle nearest the pith. But stems of certain 

 fossils — Pitys, Calamopitys, and Dadoxylon — still retain the older mesarch 

 type. In the foliage leaves of conifers the centripetal primary xylem is 

 modified to form the transfusion tissue. In the highest group, the 

 angiosperms, all trace of the old mesarch structure has vanished both 

 in stem and leaf, and the purely endarch structure prevails everywhere. 



Histology of the Wood in Species of Pines.* — K. E. Golden has 

 examinee"; thirteen species of pine, to determine, if possible, what 

 peculiarity of structure produces the variations in quality of the wood. 

 The results of the measurements of length, breadth, and thickness of 

 wall of the tracheides, the characters of the wood, including its distri- 

 bution between spring and summer formation, the distribution of resin- 

 canals, the nature of the medullary rays, and the weight, strength, 

 density, grain, and quality of the wood are given in a series of tables. 

 Examination of the figures shows that there are six species in which the 

 spring wood tracheides are longer than those of the summer, while 

 seven species have the summer tracheides the longer. The species in 

 each group show variations in hardness and strength, so that taking 

 the length of the tracheides as a factor by itself nothing can be deduced 

 in regard to the quality of the wood, but taking the length and com- 

 paring it with the width of the cells, and again comparing the width 

 -and the thickness of walls together, and the amount of the spring and 

 summer wood, the strength can be determined within limits in each 

 species. 



Pilostyles Ingas.t — W. Endriss describes the morphology and de- 

 velopment of this parasitic seed-plant. The vegetative " thallus " grows 

 in the intercellular spaces of the host-plant or penetrates its cells. The 

 flowers arise exogenously. The male contains two ring-like structures 

 with 18 to 20 pollen-sacs in each, standing above a rudimentary ovary. 

 The ovary in the female flowers contains usually five placentas bearing 

 anatropous ovules. Normal fertilisation was not observed. 



Reproductive. 



Development of the Embryo of some Dicotyledons.} — B. Schmid 

 finds that in detached seeds of Eranthis hiemalis, Corydalis cava, and 

 Ranunculus Ficaria the embryo continues its development throughout 

 the whole summer and autumn. Development depends only on favour- 

 able physical conditions, and not on any special quality of the soil. 

 Germination goes on in the open, influenced by the weather, from 

 December to March ; the seedlings are always free from mycorhiza. 



* Proc. Indiana Acad. Sci., 1901 (1902) pp. 292-7. 

 K Flora, xci. (1902) pp. 209-36 (1 pi.). 

 ; Bot. Zeit., lx. (1902) pp. 207-30 (3 pis.). 



