186 D. H. SCOTT. 



The Development q/ Articulated Laticiferous Vessels. 

 By D. H. Scott, B.A., Ph.D. (With Plate X.) 



1. Literature. 



The development of laticiferous vessels from cells was, as 

 regards certain instances, known to the younger Molden- 

 hawer ^ as early as the year 1812. At that time these 

 organs were not yet clearly distinguished from the other 

 forms of tissue which occur in the cortex ; they were com- 

 prehended, together with the sieve-tubes and soft bast gene- 

 rally, under the common name of " Vasa propria." 



The true laticiferous vessels investigated by Moldenhawer 

 were those of Musa and Chelidonium, which he found to be 

 composed of sacs which open into one another. He erro- 

 neously supposed that this also held good of the laticiferous 

 cells of Asclepias fruticosa. The anatomical investigation 

 of plants had not then made sufficient progress to render a 

 systematic study of development possible, and we can only 

 wonder that Moldenhawer came so near the truth. 



Among the more modern phytotomists, Unger, in 1840, 

 maintained that laticiferous vessels are formed by the fusion 

 of cells, but the instance he chose was unfortunately Ficus 

 benghalensis , where the laticiferous tubes are now known to 

 be inarticulated. As Unger's view was not till much later 

 supported by any trustworthy observations, it is not sur- 

 prising to find that a different theory, although wholly 

 without foundation, was long accepted by many botanists. 

 This view, according to Avhich the laticiferous vessels are 

 simply intercellular spaces which only obtain a membrane 

 of their own in the later stages of their development, was 

 first expressed by Schleiden," though not with any great 

 confidence, and afterwards, in 1846, maintained at length by 

 an anonymous authoress. ^ This intercellular theory made 

 a great impression on botanists, which is quite intelligible 

 considering that it was then the only view supported by 

 researches which were really diligent and careful, although 

 wrongly interpreted. Even Mohl^ received the new theory 



> ' Beitriige zur Analomie der Pflanzen/ Kiel, 1813, pp. 136, 140, 146, 

 151. Compare also Sachs, ' Geschichte der Botaaik,' p. 305. 



2 * Grundziige der wissenschaftlichen Botanik,' 2nd edition, 1845, part 

 I, pp. 213, 254. 



' ' Botanische Zeitung,' 184G. 



* See his ' Anatomy a?id Pliysiology of tlie Vegetable Cell,' 1852, p. 2. 



