NOTES ON RECENT RESEARCH. 



271 



with half the Jurjgermannian antheridium. Similar considerations apply 

 to the homologies of Leaf-mosses. He cites rather incomplete observa- 

 tions of Lindberg of antheridia with a necklike prolongation on the 

 female plants of the dioecious Moss, Hypnum (Brachytherium) erythro- 

 rhizum, and a similar account by Janczewski of antheridia prolonged 

 into a neck with canal-cells in Catharinea (Atrichum). He regards the 

 neck-canal- and central-cells of Pteridophytes as together equivalent to 

 the spermatogenous cells of Pteridophytes. The main differences between 

 the evolution of male and female organs are due (1) to the abeyance of 

 divisions in the female ; (2) to the sterilisation of cells in the female ; 

 (3) to the differentiation in size and function of sister-cells in the female, 

 often involving changes in space-relations. — M. H. 



Sieve-tubes. 



Sieve-tubes of Pinus, Histology of. By Arthur W. Hill, M.A. 

 (Ann. Bot. vol. xv., No. lx., p. 576). — The first mention of the sieve-tubes 

 of Gymnosperms was made by De Bary in 1877, who described and figured 

 those of Encephalartos and Sequoia. Those of the Coniferce have since 

 been examined and described by several botanists, but the conclusions at 

 which they arrived do not always agree, and a good deal of uncertainty has 

 existed in consequence on questions concerning the development and 

 the character of the means of communication between adjoining sieve - 

 tubes. The present research was therefore undertaken, first, with a view 

 of finding out which of the views (here related in a valuable historical 

 account) really agreed with the observed facts ; and secondly, whether by 

 the use of Gardiner's methods any fresh light could be thrown on the 

 development and structure of the sieve-plate. As to the first point it is 

 found that the results obtained by Bussow harmonise in the main with 

 those brought forward, for he saw that the mature sieve-plate is traversed 

 by callus-rods which enclose strings of slime. " The callus has been 

 thought by some writers to be the most important and essential part of 

 the sieve-plate, for the rods of callus were considered as the actual con- 

 necting elements ; but it seems to have been established beyond a doubt 

 from the present researches that the slime-strings, which were first 

 noticed by Bussow, afford the true and only direct means of inter- 

 communication between adjoining sieve-tubes. It remains then to be 

 seen if explanation can be offered to account for the presence of the callus- 

 rods, and whether any function can be assigned to these conspicuous and 

 invariable associates of the slime-strings." The slime-strings of Angio- 

 sperms have always been regarded as important factors in the translocation 

 of elaborated food materials, and there is no doubt, the author says, that 

 the smaller ones of the sieve-plate of Pinus perform similar functions. 

 Premising this, the explanation above alluded to is interesting, for it is 

 likely that the callus which swells so easily may be a kind of spongy lining 

 to the canals of each slime-string, and may regulate when necessary the 

 dimensions of the pores of the active sieve-plates. These slime-strings of 

 the mature sieve-plates, it may be observed, result from the conversion of 

 the protoplasmic threads of the developing sieve-plate, so all-important for 

 the transmission of stimuli from cell to cell, as well as for the passage of 



