ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 461 



heterozygotic condition of this species enables it when crossed with 

 0. biennis or a similar species, to produce two hybrids, viz. one of the 

 velutina type and the other of the Iseta type ; the hydrid-formation is 

 thus a simple Mendelian splitting. The mutants 0. nanella and 0. 

 rubrinervus behave in a similar manner. 0. gigas produces rather more 

 than 50 p.c. fertile seeds. The races of hybrids which are continually 

 appearing as the result of 0. biennis x muricata, 0. muricata x biennis, 

 and 0. Lamarckiana x biennis, and which continue to produce sterile 

 seeds until the third and fourth generation at least, are splitting hetero- 

 zygotes comparable to 0. Lamarckiana. In conclusion, the author 

 points out that investigations of hybrids similar to those described above, 

 seem to indicate that the proportion of sterile and fertile seeds is 

 constant. 



Distribution of Stomata in Gramineae.* — E. Zaepffel contributes 

 a short note dealing with the distribution of stomata in the seedlings of 

 Avena sativa, Triticum vulgar e, Panicum altissimum, and Paspalwn 

 stoloniferum. The plants examined included specimens grown in full 

 sunlight and others grown in the shade, but the same results were 

 obtained in both cases, and are as follows : — The distribution of stomata 

 is in direct relation to the power of response to heliotropic attraction. 

 The axis of the hypocotyl, which is incapable of heliotropic perception, 

 is destitute of stomata. In Avena and Triticum the stomata are most 

 numerous at the tips of the cotyledons, the region of greatest heliotropic 

 sensitiveness, while the decreasing sensitiveness towards the base of the 

 cotyledons is accompanied by decrease in the number of stomata. In 

 Panicum and Paspalum stomata are found throughout the entire length 

 of the cotyledons, but in this case every part of the cotyledon is sensitive 

 to heliotropic attraction. 



Amitosis in Root-development of Stratiotes.f— A. Arber describes 

 the structure and development of the adventitious roots of Stratiotes 

 aloides, with -special reference to amitosis. The writer's observations 

 induce her to agree with the results obtained by D. G. Scott, since she 

 finds that the apex of each young root is enclosed in a uniform cap of 

 tissue, showing no distinction between pericyclic root-cap and endo- 

 dermal digestive sac. The lacunae of the middle cortex result from the 

 varying rates of growth in the different parts of the root-tissues. The 

 most important part of the present work deals with the probability of 

 amitotic division of the nucleus of many of the cells. The root-cap, 

 cortex, and stele of the young roots exhibit a large number of cells con- 

 taining either an unusually large bi-lobed nucleus, or more than one 

 nucleus ; appearances seem to indicate that cell-walls are formed in such 

 cells subsequent to direct nuclear division. After a series of observations 

 extending over more than four years, the writer finds it impossible 

 to support those investigators who maintain that amitosis is a senile 

 phenomenon, but suggests that it "supplements karyokinesis in the 

 early development of the adventitious roots." 



* Comptes Rendus, clix. (1914) pp. 205-7. 



t Proc. Camb. Phil. Soc. xvii. (1914) pp. 369-79 (2 pis.) 



