TRANSLOCATION OF CARBOHYDRATES 281 



case. I have never seen such even in Euphorbia myrsiniks 

 which, according to Haberlandt, shows it especially well." 



The leaves were examined in chloral hydrate, by which the 

 tissues were made transparent and the tubes could be followed 

 in their entirety. They were observed to penetrate between the 

 palisade cells like hyphae, without in any way joining on to them. 

 Schimper went on to say that Haberlandt attached great import- 

 ance to the elongation of the mesophyll cells at right angles to 

 the laticiferous tubes and upon their grouping in bundles above 

 or below the tubes. 



Such elongation indicated the direction of conduction accord- 

 ing to Haberlandt, but Schimper considered that it is often 

 possible to discover purely mechanical causes for the shapes 

 and arrangements taken by cells during their development and 

 insisted that it is unwise to argue from anatomical structure 

 unchecked by experiment. He himself carried out a number of 

 experiments and, as will be shown later, these gave results 

 opposed to the value of laticiferous tubes as organs for the 

 conduction of carbohydrates. In some plants (Cichoreaceae, 

 Papaveraceae, Campanulaceae) De Bary found that the sieve- 

 tubes and laticiterous tubes were complementary in amount. 

 Where the sieve-tubes were well developed the laticiferous 

 tissue was comparatively small in amount and vice versa. From 

 this it has been thought that in cases where the laticiferous 

 tubes preponderate over the sieve-tubes the plastic materials are 

 conducted in the former, a view accepted by Haberlandt. In 

 1889 Lecomte expressed doubts about the soundness of this idea. 

 *' The widespread belief that succulents and plants with latex 

 possess smaller and fewer sieve-tubes than other plants, does 

 not appear to me to be well founded ; it has already been put in 

 doubt by M. Vuillemin as far as the stem of the Compositae is 

 concerned. In fact, in this family it is not rare to find among 

 plants with latex, sieve-tubes quite as large as in allied plants 

 without latex. Lapsana, for example, has very good sieve-tubes 

 although very rich in latex." The point was also dealt with by 

 Strasburger, who agreed with Schimper on the subject and held 

 that "... the laticiferous tubes ought not to be considered at all 

 as substitutes for the sieve-tubes, as is often stated." So it seems 

 that this question cannot be decided till further investigations 

 have been made. Again, Haberlandt and after him Pirotta and 

 Marcatili found that in many cases there appeared to be a relation 



