484 Cytologie und Befruchtung. 



Ferguson, Margaret C, The Development of the Pro- 

 thallium in Pinus. (Science. Vol. XVII. 1903. p. 458.) 



The ovules in Pinus are differentiated about three weeks 

 before pollination. There is no evidence that the megaspore 

 inother-cell originates from a hypodermal cell. The first mitosis 

 in the megaspore mother-cell is heterotypic and shows the 

 reduced number oi chromosomes. A row of four megaspores 

 is formed, the lowest always functioning. Thirty-two free nuclei 

 are formed before winter sets in, and more than two thousand 

 free nuclei were counted before cell walls begin to appear. No 

 true alveoli are formed. The „spongy tissue" is not disinte- 

 grating tissue but is a zone of physiological tissue which plays 

 an important part in the nutrition of the gametophyte. 



Charles J. Chamberlain (Chicago). 



Ferguson, Margaret C, The Spongy Tissue of Stras- 

 burger. (Science. Vol. XVIII. 1903. p. 308—311.) 



This paper consists largely of a discussion of the literature 

 dealing with the so called „spongy tissue", the active tissue 

 surrounding the growing prothallium of many Gymnosperms. 

 The writer concludes that the cells of the tissue are possibly 

 sporogenous in nature although their origin and development 

 gives no proof that this is the case. The tissue not only 

 nourishes the young prothallium but pushes before it the tissue 

 of the nucellus, thus making room for the growth of the deli- 

 cate gametophyte. Charles J. Chamberlain (Chicago). 



Hill, A. W., On the Histology of the Sieve Tubes of 

 Angiosperms. (Report of the British Association Meeting 

 at Southport. 1903. p. 854.) 



The sieve plates of the mature sieve tubes which occur on 

 the end walls of the tubes are traversed by relatively thick 

 slime strings, each being enclosed in a callus rod. In the 

 radial and tangential walls the slime strings, which are grouped 

 into oval or rounded pitted areas, are much smaller than those 

 in the sieve plates, and some three to six strings are enclosed 

 in a callus rod, connecting threads also occur between the 

 sieve tubes and the companion cells: they are very short and 

 numerous, and are usually situated in fairly deep transversely 

 elongated pits. During winter these threads may be covered 

 with callus, but only on the sieve tube side. 



Groups of fine threads occur in the membranes of the pits 

 in the lateral walls of the youngest sieve tubes, which are con- 

 verted into slime strings, the cellulose membrane in the imme- 

 diate vicinity being at the same time converted into callus; 

 thus forming the callus rod with its included slime strings. In 

 the sieve plates this action appears to proceed still further, 



giving rise to a single Iarge slime string in a callus rod. 



D. J. Gwynne-Vaughan. 



