Anatomie. 179 



the xylem sheath ; sometimes such a pocket is the first parenchyma 

 to appcar in the stele, but at other times it is preceded by the formation 

 ot' a true pith quite independent of pockets axillary to leaf traces. 

 A little higher up the pith opens into the bay of the xylem sheath 

 above the axils of every trace, forming the medullary rays; but the 

 pocket is independent of the pith, from which it is separated by a 

 hange of tracheae; the degree of development of this flange varies 

 so that the pocket may open out into the pith below the trace or 

 above the trace into the xylem sheath or more often at the level of 

 the trace into the medullary ray. The protoxylcm, when it could be 

 discerned, was usually endarch, but in several cases especially in 

 early leaves it was undoubtedly mesarch, though it became endarch 

 in the petiole. The mesarch traces being more or less oval and not 

 hollowed out adaxially leave no pocket in the cauline xylem. 



The author and Kidston in their Joint paper on the fossil Os- 

 mundaceae regarded the formation of medullary rays as due to the 

 departure of xylem elements into a leaf and the pockets more as 

 subsequent decurrent prolongations of the rays. He now considers the 

 formation of xylem-sheath-pockets as an initial cause of the medul- 

 lary ray. The pockets are believed to be associated with a gapless 

 departure of the trace; Faull, on the contrary regards the pockets 

 as portions of the central ground tissue enclosed by the centripe- 

 tal proliferation of the xylem. The internal groups of vascular ele- 

 ments found in the pith Faull regards as pinched off from the stele, 

 but as they do not seem to be connected with the outer ring at any 

 point they would seem to be reversions to vascular elements on the 

 part of the pith and as such are strong evidence against Jeff rey's 

 view that all piths are extrastelar. Further evidence against this view 

 is the presence of a pith in Zygopterid stems in which leaf or branch 

 gaps by means of which extrastelar tissues could get in have not 

 yet been found. In this case the internal phloem in Osmimdites side- 

 gateiisis and Osmanda cinnamomea and the internal endodermis in 

 Todea hymenophylloides may have arisen, in the phylogeny by 

 decurrence of the outer corresponding tissues through a branch gap; 

 or they may have been formed de novo. In the Osmundaceae and 

 in Lindsaya the pocketing is still extrastelar; in other Ferns e. g. 

 Gleichenia and Davallia we get extrastelar pocketing. 



Isabel Browne (University College London). 



Mac Alpine, D., The Fibrovascular System of the Apple 

 [Pome], and its Functions. (Linn. Soc. N. S. Wales. Abstr. 

 Proc. p. IV T . Oct. 25th 1911.) 



In a transverse section of the stalk of an apple, just as it enters 

 the fruit, there are normally ten vascular bundles — or twelve if 

 six carpels are present; eight if four — though sometimes two ad- 

 joining ones may become confluent. These, on entering the fruit, 

 spread out to form ten main trunks with numerous branches, and 

 conveniently situated midway between the skin and the centre. The 

 earliest branching and the most direct course is towards the carpels 

 and the seed; then the flesh is supplied by numerous diverging 

 branches, which unitc to form a network of vessels, and finally 

 terminate, beneath the skin, in a perfect maze of the most delicate 

 forked veinlets. By macerating an apple in a weak Solution of potas- 

 sium hydrate for a week, and then removing the soft parts in water. 

 with the aid of a brush and a needle, the fibro-vascular System may 



