258 Morphologie etc. — Varietäten etc. 



of growing above it. Each leaf is supplied with Strands from eau- 

 line bundles in different parts of the stem, consequently the Strands 

 which come from opposite sides of the stem will describe a semi- 

 circle to reach the leaf; those from the same side pass directly 

 into the leaf. Strands from intermediate points describe small arcs. 

 No cortical cambium or trace of a polystele was found. 



S. M. Hague. 



Haupt , A . W„ A Morphological Study of Pallavicinia Lyellii. 

 (Bot. Gaz. LXVI. p. 524—533. pl. 5. Dec. 1918.) 



The development of the sex organs and embryo agrees essen- 

 tially with that reported for other species of this genus. 



S. M. Hague. 



Cockerell, T. D. A., Somatic mutations in sunflowers 

 (Journ. of Heredity. VIII. p. 467—470. 1917.) 



The writer has found in his cultures of chestnut-red varieties 

 of Helianthus annuus some plants with flowerheads that in stead of 

 solid red, had a part of their ray-flowers, sometimes nearly half of 

 them, being yellow. In one case the dividing line between the two 

 colors runs down the middle of a ray. The yellow colour was not 

 very clear, but sufnsed with red. He describes them as „somatic 

 mutations", a term, he says, which does not commit us to anything 

 more than the fact of the change. It might be due to a mutation of 

 the determinor itself, but it is easier to believe that in a hetero- 

 zygous cell one of the pair of diverse allelomorphs disappeared v 

 and that this disappearance was due to a mitotic error. 



M. J. Sirks (Wageningen). 



Cook, O. F. and A. C, Polar bear cacti. (Journ. of Heredity. 

 VIII. p. 113—120. 1917.) 



In the high Andes there is a species of cactus so entirely 

 covered with long white hairs that it may appropriately be called 

 the Polar Bear Cactus. In some localities it is very abundant, dotting 

 the grassy slopes like flocks of diminutive sheep and sometimes 

 closely covering square rods of surface like a coarse, woolly blanket. 

 One of the naked forms growing at the same altitude is so closely 

 related to this shaggy form, as to be referred to the same species 

 Opimtia ßoccosa. A comparison between them shows us the great 

 advantage the shaggy cactus has by possessing its polar-bear- hairs. 

 The shaggy coat is not indispensable, but the unclothed plants are 

 much less common, and this indicates that the hair is distinctly 

 advantageous. In the atmosphere of the high lands the sun has a 

 scorching power that is probably much more trying to the plant 

 than the cold. Therefor the coat of hairs may be even more useful 

 to keep the plants from warming up too suddenly than to be a 

 protection against cold. The cooling of the plant may be somewhat 

 retarded by the hairs, but this can hardly be of as much importance 

 as the protection assured by the hairs against the injurious effects 

 of sudden exposure to the heat of the morning sun. 



M. J. Sirks (Wageningen). 



East, E. M., The explanation of self-sterility. (Journ. of 

 Heredity. VIII. p. 382-383. 1917.) 



A reply to the paper ofC. W. Moore (Journ. of Heredity. VIII. 



