ABSTRACTS 



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BOTANY. — Axillary deistogenes in some American grasses. Agxes 

 Chase. Amer. Journ. Bot. 5:254-258, figs. 1-5. 1918. 

 All the species native in the United States of three genera of grasses, 

 Triplasis, Danthonia, and Cottea, and two species from other genera, 

 Muhlenbergia microsperma and Pappophorum, Wrightii, are found to 

 produce cleistogamous spikelets in the axils of the lower sheaths. These 

 spikelets are enlarged, greatly simplified, usually 1-flowered, and with- 

 out glumes, and often so strikingly different from the chasmogamous 

 spikelets (that is those borne on the terminal panicle) of the same 

 plant, that if their source were unknown they would not be placed in 

 the same tribe. The grain of the cleistogene is usually more than 

 twice as large as that of the chasmogene. Specimens bearing these 

 deistogenes usually disjoint at the nodes, the spikelet remaining per- 

 manenth' enclosed in the sheath and the grain germinating within it. 

 In Muhlenbergia microsperma the deistogenes are inclosed in indurate, 

 greatly reduced leaf-sheaths, in shape like tiny inverted cornucopias. 

 These are produced in abundance and readily fall from the expanded 

 sheaths. Four South American and one New Zealand species of 

 Danthonia and one Siberian and one Algerian species of Pappophorum 

 are found to produce these deistogenes. All species so far found pro- 

 ducing them are plants of open ground, most of them are of arid re- 

 gions or in dry places in humid regions. Since with relatively little 

 investigation so many species have been found with deistogenes it 

 seems probable that this is not a rare habit in grasses. Any grass 

 with swollen sheath-bases and disjointing culms may repay examina- 

 tion, after the maturity of the terminal panicles. A. C. 



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