550 SUMMARY OF CURRENT RESEARCHES RELATING TO 



from water of 21° C. to water of 2*5° temperature, they contract to the- 

 extent of from 1-7 to 2*9 p.c. The difference between the longer and 

 shorter axes of the protoplasts is greatly reduced; and the process of 

 nuclear division is altogether suspended. 



Sanio's Tracheids.* — According to 0. G. Petersen, the only constant 

 and valid distinction between Sanio's tracheids and ordinary libriform 

 cells is the absence in the latter of areolated pores. If a vertical section 

 exhibits pores in the form of small lenses (lentilles), the elements in 

 question are tracheids ; if the pores have the form of striae, they are 

 libriform. This distinction refers especially to the elements of the 

 xylem. The tracheids of Conifers may be regarded as the prototype 

 of both kinds of cell in Angiosperms. 



Laticifers of Euonymus.t — L. Guignard records the occurrence of 

 laticifers in Euonymus japonicus and in all other species of the genus 

 examined. They occur in the form of latex-cells in the jmloem-region, 

 and are filled with a substance possessing properties similar to those of 

 caoutchouc and gutta-percha. The differentiation of the latex elements- 

 takes place at a late period in the stem ; in E. japonicus it is recognised, 

 at the extremity of the branches, only in the secondary tissue ; in the 

 root they appear earlier ; they are to be found in the officinal bark of 

 the root of E. atropurpureus, In none of the species examined were 

 they found in the leaf, the petiole, the pith, or the cortical parenchynie. 

 Other genera of the order Celastraceae are destitute of these laticifers. 



Secreting Apparatus of Compositae.J — M. Col commences an ac- 

 count of the secreting apparatus in the Composite, with a description 

 of the arrangement in Gazania splendens. He regards this genus and 

 Gundelia as presenting connecting links between the Cynareae and the 

 Ligulifione. Not only is the presence or absence of a secreting appa- 

 ratus inconstant in different genera belonging to the same family, but 

 different parts of the same plant may differ in this respect. Thus, in 

 Silybum mariauum, the lower part of the stem is characterised by the 

 presence of secreting canals, the upper part by laticiferous tubes. 



Stem of Dalbergia paniculata.§ — T. G. Hill describes the peculiar 

 structure of the stem of this tree from northern and central India, be- 

 longing to the Leguminosre. The peculiarity consists in the presence 

 of broad concentric masses of xylem alternating with narrow soft layers 

 of a fibrous substance. The narrow zones are of the nature of phloem, 

 accompanied by a certain amount of cambium. The phloem contains 

 well-marked sieve-tubes with sieve-plates. The xylem -masses present 

 no special character. The peculiarity of structure is attributed to the 

 formation of successive cambium rings. 



C4) Structure of Org-ans. 



Opening and Closing of Flowers. j| — A. Burgerstein gives the result 

 of a series of observations made by the late Prof. A. v. Kerner on the 



» Overs, k. Dausk. Vidensk. Selsk. Forhandl., 1901, pp. 95-108 (French abstract).. 



t Comptes Rendus, cxxxii. (1901) pp. 1354-6. 



t Journ. de Bot. (Morot), xiii. (1899) pp. 234-52; xv. (1901) pp. 166-8. 



§ Ann. of Bot., xv. (1901) pp. 183-6. 



|| Oesterr. Bot. Zeitschr., li. (1901) pp. 185-93. 



