ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 595 



found in Atriplex hortensis have the same structure until a certain stage 

 is reached, and then it seems that the method of nourishment determines 

 the final form. Transitional forms between the yellow and black fruits 

 have been found, and these also appear to depend on the food-supply. 

 The germination of black seeds varies considerably with soil and othei- 

 conditions ; in ordinary soil in the open air it is slow, and only successful 

 under favourable conditions of warmth and humidity. 



Morphology of Ambrosiacese.*— K. von Goebel contributes a few 

 notes upon the male and female inflorescences of the Ambrosiaceae. 

 Unlike the rest of the Compositse, this group is- wind-pollinated, but 

 evidence of an insect-pollinated ancestry is found in spinose thickeninfr 

 of the exine of the pollen and in the hairiness of the rudimentary 

 stigma of the male flower. The flower-structure is retrogressive, but 

 there is a tendency to develop other structures not usually found in the 

 Composit^e, e.g. the burred fruits of Xanthium.. Male capitula occupy 

 the apex of the shoot and female ones the base. The lateral male 

 capitula have flowers on the abaxial side of the axis of the inflorescence, 

 thus facilitating the scattering of the pollen ; this abnormality is prob- 

 ably due to the late development of the bract of the capitulum, and to 

 its origin from the same primordium as the axillary shoot. The male 

 flowers are arranged in the same way as in other Composit^e, but the 

 arrangement of the female flowers is dichasial. In Xanthium the 

 female capitulum consists of two flowers in a spinous envelope ; in 

 Ambrosia we find considerable retrogression ; the spines of the envelope 

 are much reduced, and the envelope itself only encloses one flower, 

 having neither calyx nor stamens and a very rudimentary corolla. The 

 author maintains that organisms become modified mainly by retrogression 

 and simplification. 



CRYPTOGAMS. 



Pteridoph.yta. 

 (By A. Gepp, M.A. F.L.S.) 



Prothallium of Anogramma leptophylla.t — B. Schussnig describes 

 and figures the development of the prothallium of Anogramma leptophylla, 

 and shows that it does, notwithstanding what Goebel has said, possess 

 an apical cell for a long while. It appears immediately after the con- 

 fervoid stage, and mostly after the formation of two so-called branch- 

 cells. Contemporaneously with the segmentation a start is made in the 

 meristematic growth of the margins of the prothaUium, which eventually 

 conceals the apical growth. The plant is a derivative from the Poly- 

 podiaceous type, but shows the family-characters in its prothallium. 

 The development of the prothallium agrees with that of Coniogramme 

 japonica, and forms a transition to more divergent types. 



* Trans, and Proc. Roy. Soc. Edinburgh, xxvi. (1913) pp. 60-8 (1 pi.), 

 t Oesterr. Bot. Zeitschr., Ixiii. (1913) pp. 97-100 (1 pi.). 



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