Ramaley: anatomy of onagraceae. 677 



carpa, sellowi and fraseri. These, she considers to be devel- 

 oped by a differentiation of the wood parenchyma. The first 

 part of her paper is devoted to an historical review of investi- 

 gations on the sieve tubes in roots occurring outside the usual 

 bast area. 



In an article on internal phloem in roots and stems, Messrs. 

 Scott and Brebner, 18 enumerate the various plant families in 

 which bicollaterality of the vascular tissue has been noted. 

 Among them is the family Onagraceae. The authors state 

 that, in general, this character is constant in each family named 

 with the occasional exception of a divergent tribe. A review 

 of Lamounette's work 19 is given in a postscript. This investi- 

 gator found, in the Onagraceae, internal phloem to be entirely 

 absent from the hypocotyl, cotyledons, and even the earlier 

 formed leaves. So far as the hypocotyl is concerned, Messrs. 

 Scott and Brebner say it can onlj T be true of very young plants. 

 We know from Weiss's observations that the internal phloem 

 is continued into the root where it forms the innermost inter- 

 xylar phloem strands. 



Intra-xylar phloem. — The presence of strands of thin walled 

 cells in the secondary wood of certain stems and roots seems to 

 have been first described by Fritz Muller 20 in 1866. This author 

 made no extended observations; he simply announced his dis- 

 covery and made a diagrammatic figure of a cross section of 

 the stem of Strychnos, a plant in which the islands are numer- 

 ous and well marked. These strands of thin walled cells, from 

 their appearance in a transverse section of the member came 

 to be spoken of as "islands." In some cases, at least, they con- 

 tain sieve tubes and so the name "intra-xylar phloem island," 

 or briefly "phloem island" was applied and is now in general 

 use. 



In DeBary's Comparative Anatomy, 21 the intra xylar phloem 

 in Strychnos is discussed, and it is definitely stated that the 

 tissue of the phloem islands is developed internally to the cam- 

 bium. A diagrammatic figure to illustrate this point is given. 



One of the earliest investigations on intra-xylar phloem, was 

 made by Weiss. 22 He found that the parenchymatous xylem of 



18 8cott and Brebner. On internal Phloem in the Root and Stem of Dicotyledons. 



Aunals of Botany 5 : 259. 1891. 



19 Lamounette. Recberches sur l'origin morphol. du liber interne. Ann. fee. Nat. 



VII. 11:193-278. 



20 Mueller. Uberdas Holzeiniger um Desterro wachseuden Kletterpflanzen.— Bot. 



Ztg. 24:65. 1866. 

 81 DeBary. Comparative Anatomy of the Vegetative Organs of the Phanerogam 



and Ferns. (English Translation.) 

 22 Weiss, loc. cit. 



