Pigott. — Notes on Nothopanax arboreum. 603 



from manv of the Umbellijerae which have reached the advanced stage 

 of having hermaphrodite and unisexual flowers in the same umbel. There 

 the hermaphrodite flowers open before the unisexual (male) ones of the 

 same umbel. In Nothopanax arboreum the outer flowers of the umbel 

 open first. Geitonogamy is here not possible, as the pedicels separate the 

 flowers too much. 



Pollen. 



The pollen-grains are boat-shaped, with three radiating grooves. A 

 few experiments were made with the pollen-grains. An attempt was made 

 to pollinate the male flowers (pseudo-hermaphrodite) with pollen from their 

 own stamens, with pollen from stamens of adjacent flowers of the same 

 umbels, from different umbels, and from different trees — with no result. 

 All fell at about the same time as the other male flowers. 



Several attempts were also made to germinate the pollen-grains in a 

 sugar solution of about 10 per cent., but none was successful. 



Flowers of the female tree were also protected with muslin to ensure 

 against external pollination. Only one of these bunches remained, held 

 by a thread of cotton, and in it the flowers had one and all withered and 

 fallen. The other bunches had, apparently, all fallen. The flowers are 

 evidently cross-pollinated. Their own stamens being functionless, these 

 flowers exhibit physiological femaleness. 



Some of the hermaphrodite buds found on the male tree were protected 

 while yet unopened, several of them being under one enclosure. These 

 opened and formed the early stages of fruit while under the muslin quite 

 as well developed as those outside. Of these hermaphrodite buds, three 

 or four only hSd withered, as had also some of those unprotected, confirm- 

 ing the opinion that some few were pseudo-hermaphrodite male flowers 

 as the normal flowers on the tree, which they closely resembled. These 

 hermaphrodite flowers all opened and spread their petals and stamens. 

 The filaments were shorter than those of the male flowers. Both petals 

 and stamens were cast off later, leaving the flower with the characteristic 

 appearance of the female flower. There is the difference here, however, 

 that pollen-grains are actually formed. 



There is no definite arrangement of hermaphrodite and unisexual flowers 

 in the umbels. In those umbelliferous plants in which there are pseudo- 

 hermaphrodite male flowers and true hermaphrodite flowers — e.g., Venus's 

 comb— the latter open first, the former not until the latter have cast their 

 stamens and petals. Directly the petals open in these hermaphrodite 

 flowers, a finely granular honey-secreting disc and two short styles are 

 revealed in the centre of the flower. The stigmas mature, but the stamens 

 are incurved like hooks. 



The fruit of the previous season remains on the tree for some time after 

 the flowers open. Later it falls in whole clusters, though the individual 

 fruits are easily detached. The receptacle is enlarged and fleshy, and 

 contains two seeds protected in a hard pericarp. 



Stamens. 



The anthers are large and versatile, 2-lobed, with two pouches to 

 each lobe. Dehiscence takes place by longitudinal slits. The inner cells 

 of each lobe are highly granular and protoplasmic. They become free 

 from their neighbours while still enclosed in their cell-walls. Each 

 mother cell forms a tetrad of pollen-grains, which are finally liberated 



