730 TRANSACTIONS OF SECTION K. 



earlier ripening seeds are adapted to an immediate germination, whilst the later 

 ones are reserved for the following spriug ? It may be that we have here tut one 

 more illustration of the operation of temperature as the limiting factor, but in any 

 case the matter wants clearing up. An experimental investigation of the rela- 

 tions of 'albuminous' and ' exalbuminous ' seeds would probably repay the trouble 

 involved. Does any condition or set of conditions under the control of the operator 

 exert an influence in this connection ? 



The mention of the early germination of seeds brings to mind the most striking 

 instance of all — that of the tropical Mangrove, in which, as is so well known, the 

 seed germinates on the tree, so that the young plant is extruded, and in some 

 instances falls, from the parent free of its envelopes. 



Our interest in this type of vegetation has been revived through the researches 

 of Mr. H. B. Guppy incorporated in his recent contribution on ' Plant-dispersal in 

 the PaciBc' This volume, perhaps the most important contribution to the biology 

 of tropical plants that has appeared since the death of the lamented Schimper, 

 is distinguished alike for its wealth of new observations and its engaging freshness 

 of treatment. There is one suggestion of Mr. Guppy's concerning the vivipary of 

 Mangroves which may occupy our attention for a few moments. 



As a result of his studies in the Paciiic and elsewhere Mr. Guppy has arrived 

 at the conclusion that the Mangrove type of vegetation is a very ancient one, 

 dating back to the times when climate was more uniform and moist than we 

 know it to-day. The viviparous habit he conjectures to have been once very 

 general, whilst to-day this primitive condition is making its last stand along the 

 tropical shores. Traces of vivipary still occur among inland plants, such as 

 Crinum, whilst in other cases it reappears intermittently under conditions not 

 fully ascertained. Mr. Guppy supposes the ordinary fruiting way of plants with 

 caducous fruits or seeds, that gerujinate after an interval, to have arisen by a 

 modification of the continuous viviparous method in the sense that the seed has 

 come to fall earlier and earlier till the stage now characteristic of practically all 

 Spermophytes has been reached. 



Piecing the data together, this seems to be the position : The earliest known 

 seeds appear to have remained on the plant just long enough to receive their 

 pollen ; but in time, it is reasonable to suppose, the advantage of remaining longer 

 was realised, and the fall of the seed was retarded till fertilisation was followed 

 by the occupation of tlie seed-cavity by an embryo. Here in seclusion the embryo 

 could remain until germination was convenient. Starting at the other end, our 

 modern seed, according to Mr. Guppy, has been evolved by the gradual retention of 

 the viviparous embryo ; or, to put it in another way, the detachment of the seed 

 has been hastened so that it falls long before germination is due. 



Well, these theories fail to meet in the middle, as they should if they are to 

 present us with an epitome of the whole seed-history. Perhaps there were 

 troublous times in that middle epoch, so that the continuity has become obscure ! 

 Or possibly another view may be admissible of the relation of vivipary to normal 

 seed-production. Most botanists, I take it, have been inclined to regard vivipary 

 as the dernier cri in seed-history, the ultimate stage in the way of possible repro- 

 ductive advance in seed-bearing methods that the higher plants have yet attained. 

 The Mangrove process might even be conceived as the starting-point, under certain 

 contingencies, of a whole new race of plants with life-histories complicated by 

 fresh alternations — homologous alternations — far beyond any of which we have 

 knowledge to-day ! 



Schimper and others who have given attention to the subject found no reason 

 for regarding vivipary as other than an adaptation to special circumstances, an 

 extreme condition that had arisen independently in several cycles of affinity. 

 Before the contrary can be accepted a good deal of positive evidence will be 

 needed, drawn from the non-Mangrove representatives of groups in which 

 vivipary occurs, to show that the relationship is other than has been generally 

 supposed. Moreover, if the viviparous habit were formerly of wide occm-rence 

 some traces of it might reasonably be expected in the fossil record. So far as can 

 be ascertained, such have not been forthcoming, nor can I hear of any record of 



