326 SUMMARY OF CURRENT RESEARCHES RELATING TO 



On the Size of the Nucleus.* — J. J. Gerassimow describes in detail,, 

 with tables, his observations on cells of Spirogyra, which, by abnormal 

 conditions (cooling, etherisation, etc.), have been caused to divide into 

 cells without nuclei and cells with either a single very large nucleus or 

 two nuclei. 



Structure and Development. 



"Vegetative. 



Course of Laticiferous Tubes in Leaves.f — Oscar Mayus has studied 

 the laticiferous tissue in the leaves of members of the Moracese, Papa- 

 veraceas, Euphorbiacese, Apocynaceas, Asclepiadacea?, and Composite 

 and comes to the following conclusions : — The laticiferous tubes in the 

 leaf-blade form, with those present in other parts of the plant, a 

 perfectly continuous system. Latex-tubes, peculiar to the leaf, do not 

 occur. Generally, the latex- tissue accompanies the vessels ; from this 

 point of view we can distinguish three classes of latex-tube endings : 

 (a) the tubes end along with the vessels ; (b) they pass beyond the vas- 

 cular bundle and run free in the parenchyma ; (c) they run from the 

 lower to the upper epidermis of the leaf. In addition to H and net-like 

 anastomoses, those of loop-form also occur. From the nerves of the 

 third order onward, latex-tubes take the place of sieve-tubes. Starch is 

 always present in the cells surrounding the free running latex-tubes. 



Structure and Development of Epiphegus virginiana.+ — E. Cooke 

 and Schively have made a study of this parasite, a member of the 

 Orobanchacese. They find that the haustoria are not developed on the 

 parasite, but arise from the roots of the beech, the host-plant. The 

 embryo is rudimentary. Bicollateral bundles occur both in the tuber 

 and in the aerial shoot. 



Secretory Apparatus of the Dipterocarpese.§ — P. Guerin has studied 

 the mode of development and the course of the secretory canals in the 

 wood of species of Bipterocarpus. The canal arises by separation of four 

 cambial cells, which are precisely like the other elements of the cambium* 

 and, contrary to the method of development usual in other plants, these 

 four cells do not result from the division of a single mother-cell. The 

 canal may retain this original form, or it may be found at a later stage 

 bordered by a larger number of cells, the increase in the number being 

 due not to a radial division of the original four, but to their tangential 

 separation, whereby a larger number of cambial cells is involved. The 

 diameter of the canal hardly increases with age, but at a given time, the 

 thin walls of the secreting cells which limit the canal give way, and the 

 original border more or less completely disappears. Tangential sections 

 show an anastomosing between some of the canals during their sinuous 

 longitudinal course. 



Pitcher-formation in Saxifrages.||— J. Mahen and X. Gillot have 

 studied the teratological formation of pitchers in Saxifraga ciliata, in 



• Beih. Bot. Centralbl., xviii. (1904) pp. 45-118 (2 pis.), 

 t Tom. cit, 1905, pp. 273-86 (17 figs, in text). 



% Contr. Bot. Lab. Univ. Pennsylvania, ii. (1904) pp. 352-98. See also Bot 

 Gazette, xxxix. (1905) p. 239. § Comptes Eendus, cxl. (1905) pp. 520-2. 



|| Journ. de Bot., xix. (1905) pp. 27-39 (7 figs in text). 



