ZOOLOGY AND BOTANY, MICROSCOPY", ETC. 663 



is derived from the lowest megaspore, i.e. the one at the chalazal pole, 

 because the divisions which give rise to the megaspores are such as to 

 give the larger proportion of plasma to that cell owing to its more 

 favourable position with reference to the source of nutriment. This 

 view is supported by the Rubiacese in so far that the larger number of 

 megaspores and undivided megaspore mother-cells form a nutritive 

 tissue, surrounding more or less completely the embryo-sac cell which 

 arises near the longitudinal axis of the mass. The fact that in forms 

 in which a pluricellular sporangium is present any or all of the mega- 

 spores can develop into embryo-sacs proves their morphological equality, 

 and the regular division of each of the megaspore mother-cells into 

 four must be regarded as a true tetrad division. 



The author compares Murbeck's results in Alchemilla, where the 

 archesporium is multicellular; some of the mother-cells never divide 

 and never give rise to embryo-sacs, the others divide once or twice, 

 forming megaspores, two or more of which may develop into young 

 embryo-sacs, aud in the same sporogenous cell-row two or more may 

 commence their development into embryo-sacs. This is precisely com- 

 parable with Crucianella in Rubiacese. The pluricellular archesporium, 

 which has been shown to occur in widely separated families, has no 

 phylogenetic significance; the meaning is purely physiological. The 

 archesporial tissue not directly concerned in the formation of the 

 embryo-sac takes actively or passively a nutritive role, either gradually 

 disintegrating and becoming absorbed, or growing, chiefly in length, 

 and forming a transporting tissue connecting the embryo-sac with the 

 vascular supply of the ovule. The embryo-sac may develop in situ or 

 break through the nucellar cells and pass along the micropylar canal, 

 deriving nutriment from the adjacent disintegrating cells. The antipodal 

 cells in the Galiese are three in number, one being much elongated, its 

 free end plunging into the mass of disintegrating megaspores and 

 acting as an absorbent organ. In Crucianella they are short-lived and 

 show no special development. In Diodia virginiana there are from 4 

 to 10, arranged in a long series and physiologically equivalent to the 

 single long antipodal in the Galiese. The author points out that the 

 form and cytological structure of the antipodals, the changes in their 

 food content, their tending to multiply and form a special conductive or 

 nutritive tissue, supports Westermaier's conclusion that the antipodals 

 form an anatomical-physiological apparatus, and not a useless rudi- 

 mentary structure which may be understood only from the view of com- 

 parative morphology. 



The embryo in the Galiese has a highly developed suspensor, the 

 cells of which elongate laterally, forming haustoria which penetrate 

 between the cells of the endosperm ; the suspensor therefore acts as a 

 temporary embryonic root. This condition is analogous to that de- 

 scribed by Dickson in Tropseolum, where the branches from the base of 

 the suspensor penetrate the pericarp. Similar organs have been de- 

 scribed by Treub in Orchidaceae, and by Hofmeister and Guignard in 

 Leguminosae. In the Spermacocese and Houstonia there is a complete 

 absence of these adaptive characters ; the suspensor is a very simple 

 structure. The peripheral cells of the endosperm, from their cyto- 

 logical character and the behaviour of the adjacent tissues, may be 



