536 dufrenoy: metaphanic variation in grasses 



We found them to apply fairly well to the case of Dactylis 

 glomerata. 



Two forms of Dactylis glomerata have been described, the true 

 D. glomerata with a dense inflorescence, the branches at its base 

 being less than 5 mm. long, and D. glomerata ramosa with a 

 divided inflorescence, the basal parts being supported by branches 

 10 to 60 mm. long. The specialized character of D. glomerata 

 is the suppression of the basal branches in the inflorescence, the 

 whole inflorescence being the homologue of the terminal in- 

 florescence of D. glomerata ramosa. This latter, which is less 

 differentiated, may be considered an ancestral form. 



In a meadow at Bareges (Hautes-Pyrenees, France) careful 

 examination of hundreds of D. glomerata and D. glomerata ramosa 

 led to the discovery: (1) of two inflorescences, bearing sterile 

 spikelets, to be compared with the sterile ear of Zea tunicata; 1 

 (2) of a case of metaphanic variation which is most remarkable 

 as it actually brings to light ancestral characters. 



Green foliage organs, 23 to 25 mm. long, developed between 

 the glumes, some of which yielded cf and 9 reproductive 

 organs. Some of the foliage organs enclosed normal, rudimen- 

 tary, or abnormal stamens and pistils, or rudimentary leaves 

 developed where pistils should have been. These metaphanic 

 variations may be compared with those observed by Collins 

 in the terminal inflorescence of full tunicate plants of maize. 

 Successive transverse sections displayed all gradations in the 

 forms of cf reproductive organs from the microsporangia of 

 thallophytes to the stamens of flowering grasses. 



Twelve microsporangia were imbedded in the parenchymatous 

 tissue at the base of the foliage organ, which was thus a true 

 homologue of the thallus of nonflowering plants. Some of these 

 microsporangia were rudimentary and contained cells scarcely 

 different from the parenchymatous neighboring cells, while 

 others contained pollen-grains surrounded ■ by nutritive cells. 

 In the upper sections these microsporangia became more and 

 more individualized and were freely grouped two by two as 

 stamens. 



1 Collins, G. N. Journ. Agr. Research, 9: pi. 15. 



