THE PALM-STEM. 29 



cotyledons, regarded them as prosenchymatous cells, and 

 distinguished them neither from the liber nor the wood. 

 In a longitudinal section we perceive that the cells are 

 elongated in these bundles, and stand one above another 

 mostly with horizontal septa ; the septa are, however, 

 sometimes oblique, and the tubes not unfrequently ter- 

 minate in a point. We may distinguish narrow and wide 

 cells, frequently with a tolerably strong difference of 

 diameter. Moldenhawer (Beitrage, p. 126) regarded the 

 wider tubes as cells of the usual kind, and the narrow as 

 proper vessels, which he referred to the same system as 

 the milk-vessels of Chelidonium, Asclepias, &c. So far 

 as my own investigations showed, I cannot agree with 

 Moldenhawer in this distinction of wide and narrow 

 tubes, for I frequently believed that I saw both contain- 

 ing an opaque, thickish sap, in which swam a great 

 abundance of fine granules ; I am, therefore, compelled 

 to refer both to the same system. I never found the 

 contained sap milk-white, but only more or less opalescent. 

 I never could observe any currents, but only an oscilla- 

 tion of the minute granules, which appeared to me merely 

 molecular motion. The septa between the tubes are 

 completely closed. In the stem, the wide and narrow 

 tubes are intermingled without order in the entire bundle, 

 but a different condition will be met with in the root. 

 In Calamus, the bundle of these proper vessels is not 

 only divided into two separate portions, but the narrower 

 tubes are frequently separated from the wider, as the 

 latter often lie isolated, at the limit between the wood- 

 and liber-cells. 



I have denominated these tubes proper vessels, because 

 the nature of their contents brings them nearest to the 

 system known as the vital (Lebensgefasse) or milk-ves- 

 sels ; I shall bring proofs further on that they are different 

 from this system. In reference to their development, 

 I can merely state that, in the Palms as in other Mono- 

 cotyledons, they precede the formation of the woody por- 

 tion in so far that, when a fibrous bundle devoid of vessels 



