ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 297 



Structure and Development. 



Veg-etative. 



Spiral Vessels and Growth in Length.* — G. Bonnier and J. 

 Friedel contribute a note upon the rehitions which may exist between 

 growth in length and the number of spiral vessels present in tlie root 

 and stem. It is shown that usually the annular and spiral vessels are 

 more numerous in the stem than in the root ; that they are capable of 

 elongation, and but slightly attached to the cell- wall in the stem, while 

 these conditions are reversed in the root ; also that the elements composing 

 the spiral vessels of the stem are more elongated than in the root. 

 Examination of the wood of stems of various trees shows that spiral 

 vessels similar to those usually found in roots are characteristic of stems 

 which have terminal but. not intercalary growth. A similar condition 

 is seen in the structure of the hypocotyl. In Fisum sativum, where 

 the hypocotyl does not increase in length, the spiral vessels are pooTly 

 developed. In Fhaseolus multiflorus, where there is slight increase in 

 length, the spiral vessels are better developed ; while in Phaseolus 

 vulgaris and Lupinus albus, where there is considerable elongation of 

 the hypocotyl, the spiral vessels are well developed. It would thus 

 appear that the histology of the vessels is connected not with the anatomy 

 but with the mode of growth. 



Structure of Tuberous Melastomaceae.t — H. J. de Cordemoy con- 

 tributes a note upon two new species of Melastomace^e found in the east 

 of Madagascar, viz. Medinilla tuberosa and M, ruhrinervis. Both 

 species bear a strong morphological and anatomical resemblance, but 

 differ in the nature and distribution of the reserve-materials, e.g. cellu- 

 lose, amidon, tannin, etc., stored in the stem or tubers. Such reserves 

 are exceptional in this family, and are doubtless the result of adaptation 

 to an epiphytic life. The tuberized roots must be regarded as organs 

 adapted for the storage of water. 



Mechanical Tissues of the Umbel liferse.^ — G. Funk has studied 

 the leaves and stems of a large number of species belonging to the 

 Umbellifer^e, and finds that the mechanical tissues are at first composed 

 of collenchyma, and that they retain this character as long as there is 

 any growth. In Silans and Heradeum the main axis does not exhibit 

 the typical structure of its peripheral mechanical system until just 

 before the opening of the flowers of the terminal umbel ; the collen- 

 chyma-cells of the lower internodes then begin to lignify. In (Enanthe 

 Hgnification is not complete until the fruit is half ripe. In order to 

 fully understand the stem structure of the Umbelliferae, it is therefore 

 necessary to study the stems of mature plants, and the author believes 

 that the numerous divergences in current descriptions are due to the 

 use of immature specimens. 



It appears that there are two distinct classes of lignified tissues ; in 



* Rev. g6n. de Bot., xxiv. (1912) pp. 385-91. 



t Comptes Rendus, cliv. (1912) pp. 1523-5. 



X Beih. Bot. Centralbl., xxix. (1912) pp. 219-97 (5 pis.). 



