ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1013 



as metamorphosed leaf-rachis. This is well shown iu transitional 

 forms between tendril and leaf in Cucurbita Pepo. 



In Cyclantliera pedaia the sensitiveness is far more intense than 

 in any species that has hitherto been described. The circumnntation 

 is completed in from 39 to 75 minutes, the average being 54. Curva- 

 ture begins to take place after contact with the under side with a 

 solid body for nine or even for five seconds; and 15 minutes suffices 

 for the tendril again to become straight after the irritation has 

 ceased. The temperature and degree of moisture of the air do not 

 appear sensibly to affect the sensitiveness. Spiral coiling begins in 

 5 and is completed in from 8 to 10 hours, while the portion which 

 embraces the support increases two to three times in diameter, and 

 becomes hard and brittle. 



Tendrils which become attached to the support by a mucilaginous 

 excretion occur not only in several species of Tticliosanthes, but also 

 in Sicyos angidatus. In all the species examined the tendril becomes 

 thicker where in contact, but only on the under side. Statements of 

 the contraction of the concave side rest on inaccurate measurements. 



Dr. Muller dissents from the ordinary explanation of the curva- 

 ture of tendrils, that it results from unequal growth of the two sur- 

 faces. It depends rather on their anatomical structure. Wherever 

 this is central the tendrils exhibit no power of curvature, but only 

 where the structure is bilateral. All the constituents which readily 

 undergo change are collected on the convex, the firmer ones on the 

 concave side. As long as tendrils are strongly sensitive the scleren- 

 chyma does not become liguified ; this finally takes place in the 

 whole of the parenchyma of the clinging portion. 



In a further note on this subject * M. P. Duchartre maintains, in 

 opposition to the statements of Darwin, that even when it has not 

 caught hold of any support, a tendril may coil in two, three, or even 

 four successive spirals in opposite directions. He further states that 

 in Cucurbita Pepo the formation of the spiral results directly from an 

 important modification of structure which causes the disappearance, in 

 the half of the organ which becomes external, of the fibrovascular 

 bundles ; the large-celled medullary parenchyma attaining, at the 

 same time, special development in that portion. This change in the 

 disposition of the vascular bundles Duchartre believes to be a general 

 phenomenon in the Cucurbitaceaa ; he finds it also in Ecltinocysiis lobata 

 and Cyclantliera p'edata. The latter species is distinguished by the 

 remarkable projection of the two horns of the crescent, which forms a 

 section of the tendril in its twining portion. 



Changes in the Perianth during the Development of the Fruit.f 

 — Herr C. Reiche has examined the mode in which the perianth is 

 thrown off after withering in plants belonging to 45 natural orders. 

 It may take place in three different ways, viz. — (1) By the formation 

 of a small-celled separating zone, usually coinciding with the place of 

 insertion of the perianth ; in the Nyctagineae a portion of the perianth 



* Bull. Soc. Bot. France, xxxiii. (188G) pp. 157-69. Cf. this Journal, ante, 

 p. 823. 



t PriDgsneini's Jahrb. f. Wiss. Bot., xvi. (1885) pp. 638-87 (2 pis.). 



