46 Biologie. — Morphologie und Teratologie. 



Verf. sieht die in Rede stehenden Gebilde weder als sterile 

 Stamina, noch als Commissuren, noch als Nebenblätter, sondern 

 als Organe sui generis an, die bei jeder Species constante Form 

 und ontogenetisch gleichen Werth wie die übrigen Blüthentheile 

 besitzen. Eine Discussion der verschiedenen Einzelfälle ergiebt, 

 dass, wenn nicht überall, so doch bei einer grossen Anzahl von 

 Amarantaceen Autogamie verbreitet ist. Die Staminodien spielen 

 dabei als secundäre Hilfsmittel zur Bestäubung eine Rolle, in- 

 dem sie dazu beitragen, dass der Pollen an die rechte Stelle 

 gelangt und zwar, wo lange Narbenschenkel vorhanden sind 

 an die Basis dieser Schenkel, wodurch der Weg des Pollen- 

 schlauchs verkürzt wird (Gomphrena chloromalla Lopr.). Die 

 Verwendung der Staminodien in der Systematik der Amaranta- 

 ceen erfordert Vorsicht, weil ihr Auftreten wohl bei den ein- 

 zelnen Arten, nicht aber in den Gattungen constant ist. Eine 

 Revision der Genera mit Rücksicht auf die Staminodien könnte 

 vielleicht neue Beziehungen einiger einfacherer Typen und 

 monotypischer Gattungen ergeben. Büsgen. 



Darbishire, 0. V., Observations on Mamillaria elongata. 

 (Annais of Botany. Vol. XVIII. july 1904. No. LXXI. 

 p. 375-416. PI. XXV— XXVI.) 



In addition to a consideration of the general morphology and ana- 

 tomy the author deals especially with the structure of the tubercles, their 

 morphological nature and their function. The tubercles are found to re- 

 present the leaf-base (and possibly also a portion of the stein), whilst 

 the species are modified portions of the leaf-blade. There is only one 

 bud (i. e. an axillary one in the axil of the tubercle in connexion with 

 each tubercle or leaf. The vascular System of the root consists of annular 

 tracheids throughout^ which in the stem are replaced by special Clements. 

 One Strand of vascular tissue leaves a bündle of the main stem for 

 every tubercle; this branches freely with anastomosis of the branches in 

 the cortex and in the tubercle (where it forms a cortical and a medullary 

 System) and finally eids in a large cup-like mass of big tracheids, 

 whereas the lateral brauch on leaving the main bündle consists of ex- 

 tremely minute spiral tracheids. The apex of the whole tubercle is 

 occupied by a cushion of cork-tissue, in which the spines are inserted. 

 Within the colourless epidermis of the tubercle except. at the apex we 

 find a hypoderm of ilat short cells, which is succeeded by rows of pali- 

 sade cells, making a definite angle with the epidermal layer, this angle 

 being apparently determined by the direction of the ir.cident light; abun- 

 dant chioroplasts occur in the palisade cells. The cap-like ending of the 

 bundle-system of the tubercle is immediately surrounded by large and 

 clear cells with large vacuoles; these no doubt exert a strong osmotic 

 action on the water contained in the neighbouring tracheidal Clements. 

 The extensive air-spaces, bordering the carbondioxide absorbing cells, 

 do not separate them very much ; the narrow diameter of these species 

 hinder transpiration, while not interfering with the photosynthetical func- 

 tions of the green cells, for according to the work of Brown and 

 Escombe the small width of the air-spaces is rather favourable to the 

 rapid introduction of CO2. The air immediately outside the fleshy part 

 of the plant is kept more or less stagnant by the passive action of the 

 spines, which in their entirety form a fairly complete screen surroun- 

 ding the plant; the temperature of the air in the plant is considerably 

 Iower than that outside, so that there is no rapid current of air outwards 



