194 D. H. SCOTT. 



On the Laticiferous Tissue of Manihot 

 Glaziovii (the Ceara Rubber). 



By 



]>. H. Scott, M.4., Pb.D., 



Assistant to the Professor of Botany in University College, London. 

 (From the Jodrell Laboratory, Kew.) 



With Plate XVll. 



In the course of some work on the development of laticifer- 

 ous tissue in the secondary cortex I was led to examine the 

 Ceara Rubber (Manihot Glaziovii), a plant to which my 

 attention was first directed by Mr. Thiselton Dyer. The in- 

 vestigation of this plant has led to some very unexpected 

 results, which it is the object of the present paper to commu- 

 nicate. 



It has hitherto been assumed, expressly or tacitly, that in 

 those families which possess any kind of laticiferous tissue 

 the articulated and the non-articulated forms mutually ex- 

 clude one another. Thus, De Bary ^ states that " each of 

 these categories is peculiar to definite families," while the same 

 conclusion follows from Sachs' treatment of the subject in his 

 ' Textbook ' ^ and ' Lectures.' ^ Although it is well known that, 

 in the same family, genera with and without laticiferous tubes 

 may occur, as in the Papaveracese and Aroideae,^ yet, where 

 present at all, this tissue has hitherto been found to be of uni- 



' ' Vergleichende Auatomie,' p. 195. 

 -' 2nd Eng. ed., pp. 85, 86. 

 » ' Vorlesungen,' pp. 206, 207. 

 < De Bary, 1. c, pp. 450, 451. 



