558 SCIENCE PROGRESS 



occur in the midrib and principal veins of some dicotyledonous 

 leaf-blades, so that their presence outside the midrib in the 

 " laminse " of Monocotyledons may be regarded as indicative 

 of a phyllodic origin. Sixty-two genera belonging to thirteen 

 families are recorded from the Monocotyledons in which such 

 inverted bundles have been recognised. It may be noted that 

 these include the " pseudo-lamin e " of Sagittaria, Hydrocharis, 

 Eichornia, Heteranthera, and Pontederia. The feature is most 

 frequent in the Helobiae, Liliiflorae, and Farinosas. Some 

 years ago the reviewer showed that there is good reason for 

 regarding the amount of vascular tissue in the petiole as 

 definitely related to the transpiring activity, whilst the arrange- 

 ment of the vascular strands appears to depend largely on 

 mechanical considerations. Where there is little or no cambial 

 activity, the strands are more numerous, which, owing to special 

 relations, may result in the presence of inverted bundles. Be- 

 fore, therefore, one can accept the anatomical structure as 

 indicating a phyllodic origin, it will be necessary to establish 

 that the former is not the outcome of physiological needs. 



Genetics. — A. St. Clair Caporn contributes three papers to 

 the Journal of Genetics (Aug. 191 8), of which the first two deal 

 respectively with the inheritance of " tight " and " loose " 

 paleae and early and late ripening in oats. With regard to 

 the former, Avena nuda was crossed with three varieties of the 

 common oat all characterised by tight paleae in contrast to the 

 loose paleae of A. nuda. In the latter, however, " tight " 

 grains may be as numerous as 40 per cent., pure " tight " forms 

 never having been obtained. In extracted pure " tights " the 

 number of grains in the spikelet never exceeded four, whilst 

 in A. nuda their number varied from six to ten. In the second 

 paper the author agrees with the results of Hoshino (Imp. 

 Univ. Sopposo Japan, 191 5) on peas and rice in regarding 

 early and late ripening as Mendelian characters, probably, 

 however, dependent on three factors. In F3 a comparatively 

 early type is segregated. The third paper deals with crossing 

 of Triticum polonicum (av. glume length 29*23 mm.) and 

 T. eloboni (av. glume length 10*58 mm.). In the Fi genera- 

 tion the glumes were of intermediate lengths. In F2 the varia- 

 tion curve for glume lengths shows three periods representing 

 the overlapping curves for homozygous long, homozygous short, 

 and heterozygous intermediate forms, An interesting feature 



