ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 81 



Sieve-tubes of Cucurbita.* — According to A. Fischer, a transverse 

 section of an internode of Cucurbita shows two systems of sieve-tubes, 

 one belonging to the vascular bundles, and the other situated within 

 the sclerenchymatous ring so characteristic of the Cucurbitaceas, 

 which lies beneath the strongly developed coUenchymatous tissue. 

 This occurrence of sieve-tubes in the cortex is, as far as is at present 

 known, entirely confined to this order. The sieve-tubes of the 

 separate vascular bundles are united into one system with one another 

 and with those of the cortex for the conveyance of nitrogenous 

 formative materials, by fine transverse uniting strings which press 

 through the fundamental tissue. On the other hand the peripheral 

 sieve-tubes can only be in communication with this system through 

 the nodes, as no uniting strings have been observed to pass through 

 the sclerenchymatous ring, which is closed on all sides. 



Spines of the Aurantiaceae.t — J- Urban has investigated the 

 morphological value of the spines, which occur singly or in pairs, in 

 the axils of the leaves of many but not all Aurantiaceae, and which 

 have been generally regarded as metamorphosed axillary shoots. 

 From comparison with unarmed species, and from the history of 

 development, Urban regards them, on the contrary, as the meta- 

 morphosed lowermost leaves of the primary axillary shoot. Inter- 

 mediate forms are exhibited by some species of Citrus. 



Tubers of Myrmecodia echinata.J — M. Treub describes the re- 

 markable tuberous stem of the epiphytal Rubiaceous genera Myrmecodia 

 and HydnojpJiytum, which are permeated by passages inhabited by 

 immense numbers of ants. He states that the passages are not 

 burrowed by the ants, but are formed by the disappearance of cells 

 which become entirely enveloped in layers of cork. Their object is 

 not to protect the colonies of ants, or to supply them with food, but 

 rather to facilitate communication between the inclosed air-spaces 

 and the external atmosphere. 



Chlorophyll-grains, their Chemical, Morphological, and Bio- 

 logical Nature.§ — A. Meyer continues his previous investigations on 

 this subject. II 



He expresses a strong opinion against the chlorophyll-grains 

 being surrounded by a membrane. Where a denser portion becomes 

 separated on contact with water, this must not be regarded as 

 originally present ; for if so, it would become thinner by the swelling 

 of the surrounding protoplasm, or by tensions resulting from endos- 

 motic action, which is not the case. Pringsheim's lipochlor and 

 hypochlorin he regards as still hypothetical. 



Observations on Acanthephippium and AspJiodelus show that the 



* Ber. Deutsch. Bot. Gesell., i. (1883) pp. 276-9. 



t Ibid., pp. 313-9 (1 pi.). 



X Ann. Jard. Bot. Buitenzorg, iii. pp. 129-60 (5 pis.). See Bot. Centralbl., 

 xvi. (1883) p. 103. 



§ Meyer, A., ' Das Chlorophyll-korn, in chemiscJier, morphologischer, n. ■ 

 biologischer Beziehung ' (3 pis.). Leipzig, 1883. See Bot. Centralbl., xv. (1883) 

 p. 382. 



II See this Journal, iii. (1883) p. 239. 

 Ser. 2.— Vol. IV. a 



