14 Mr M. C. Potter, On the increase of the thickness [Nov. 11, 



(2) On the increase in thickness of the stem of the Cucurbitacece. 

 By M. C. Potter, M.A., St Peter's College. 



The Order Cucurhitacem consists for the most part of her- 

 baceous plants climbing by means of tendrils; like many other 

 climbing plants, the members of this order have an anomalous 

 distribution of the fibro-vascular bundles in the stem; the bundles 

 being arranged in two concentric rings, and each individual bundle 

 being bicollateral, with phloem both on its external and internal 

 sides. (Fig. 1.) 



The structure of these stems was first described by Hartig* 

 and then by von Mohl*f" and has been the subject of investigation 

 by various botanists, most of whom have confined their attention 

 to the structure and contents of the sieve tubes. Bertrandj how- 

 ever has described the manner in which a cambium between the 

 xylem and both inner and outer phloem adds respectively both 

 xylem and phloem to the bundle, whilst Petersen §, in his article 

 on Bicollateral Bundles, gives a short account of the increase of 

 the stem of Zehneria suavis; stating that there is no interfascicular 

 cambium, but that while the bundles increase the cells of the 

 medullary rays increase passively in a radial direction and finally 

 divide. With this statement de Bary || agrees. Fischer If also 

 says that there is no interfascicular cambium present whereby 

 these stems can increase in thickness. The fact that all the 

 investigated species of Cucurbitacem have been herbaceous ex- 

 plains why the interfascicular cambium has hitherto not been 

 described. 



Lately I have had an opportunity of investigating the woody 

 stems of Cephalandra indica (Naud.), Trichosanthes villosa (Bl.) and 

 T. anamalayana (Bedd.), and find that they increase by a well- 

 marked interfascicular cambium. The stems of these plants agree 

 with those of the other members of the order in possessing the 

 two rings of bicollateral bundles (fig. 1), but differ in having no 

 ring of sclerenchymatous tissue between the epidermis and vas- 

 cular bundles. The structure of these species being similar in all 

 respects it will only be necessary to describe the stem of Cepha- 

 landra indica. 



Cephalandra indica, a climbing woody plant, reaches to a 

 considerable height and its stem, which is perennial, attains to 

 several inches in diameter. In its young stage the stem contains 



* Bot. Zeit. 1854. 



t Bot. Zeit. 1855. 



J " Theorie du faisceau," Bull. Sci. du departement du Nord, 1880. 



§ Eiigler Bot. Jahrb. vm. p. 374. 



|| Comparative Anatomy, English edition, p. 456. 



it TJntersuchungen iiber das Siebrohreii-system der Cucurbitaceen, p. 6. 



