PARTHENOGENESIS. 467 



occurring on the female plants (c/. p. 300) has not been ignored, but they have 

 never been detected on the plants used for observations; consequently its own 

 pollen has never had access to the stigmas of the plants in question. In spite 

 of this, ripe seed has been obtained and new plants raised from it, which, in their 

 turn, bore only female flowers. Nor do these new plants differ in any way from 

 the plant originally introduced; this observation is of importance, as it might be 

 suggested that they were hybrids, that the pollen of some other euphorbiaceous 

 plant had reached the stigma, there produced pollen-tubes and fertilized the ovules 

 of Coelebogyne. But this is not so, otherwise the offspring would give some indica- 

 tion of such origin. And the plant itself gives indication that it is not fertilized 

 by any pollen. If a plant of Coslehogyne be kept apart where no pollen has access 

 to it, it can be noticed that its stigmatic lobes remain quite fresh for a long time, 

 even till the ovary begins to swell. Only later do they fade, when the seeds are 

 well advanced. This observation is of value since in ordinary cases the stigmas 

 fade very soon after pollination, and it is only unpollinated stigmas which retain 

 their freshness (cf. p. 285). In view of these oft-confirmed results, from which 

 all possible source of error has been eliminated, we may conclude that the ovules 

 of Coslehogyne ilicifolia are able to produce embryos without the co-operation of 

 the male protoplasm. 



We may now consider whether the instances just described can be regarded 

 as cases of true fruit-formation. As the essence of fruit- formation is a union 

 of ooplasm and spermatoplasm, or in other words, fruit-production must be pre- 

 ceded by fertilization, and as this condition is not fulfilled, these structures are 

 not true fruits. In the absence of fertilization, we must regard these reproductive 

 bodies as brood-bodies, or a special form of offshoot. As has been previously 

 mentioned (p. 44), brood-bodies can arise from any portion of a thallus, from any 

 portion of the stem, and from leaves of the most various kind. A brood-body 

 can originate from the protoplast of a cell of a Lichen-thallus or of a Moss-leaf, 

 from one in the root of an Ash-tree or in the stem of an Orange Lily, on the 

 margin of an Orchid-leaf, or over the midrib of a Begonia-leaf; whj^ not also 

 from the protoplast in the oogonium of Chara crinita, or in the archegonium 

 of a Moss, and in the ovules of Gnaphalium alpinum, Mercurialis annua, and 

 Coelebogyne ilicifolia 1 Experience shows that in the great majority of cases, 

 both in the Cryptogams and in the Phanerogams, the young commencements of 

 the fruits abort if the ooplasm be denied the spermatoplasm which should fertilize 

 it; but it also shows in unmistakable manner that in a few plants the ooplasm 

 does not die even in the absence of fertilization. 



Without entering upon profitless speculations belonging to the domain of 

 Nature-philosophy, we may discuss the question of the possible reasons for the 

 curious behaviour of the " fruits " in these cases. And first of all it may be 

 observed that all the plants exhibiting the phenomenon of parthenogenesis are 

 dioecious. For such plants a crossing with other individuals is alone possible. 

 But what occurs should a crossing in such plants be impeded from any cause ? It 



