I50 NATURAL SCIENCE. September. 



' leaf '-like petal to the anther-bearing filament. Double-flowers and 

 monstrosities delighted us, for in them we saw a harking back to the 

 original form. If we imagined anything of evolution it was an ordinary 

 foliage shoot, becoming in course of ages converted into a flower, 

 perfect and complete. , And after all we found nothing in our text- 

 books, and heard nothing at our lectures, to contradict our little 

 theory. 



The outer series, the sepals and the petals, were concerned mainly 

 with the protection of the ' essential ' stamens and carpels, or with visits 

 of insects and other creatures associated with the deposition of pollen 

 on the stigma. The pollen-sacs of the stamen, and the ovules borne 

 by the carpel, were sporangia comparable with those borne on the 

 fertile leaf of a fern, or the sporophylls of an Equisetum. But when we 

 came to study ' types," beginning with the unicellular plant, and 

 working upwards, doubts would sometimes arise. Our series of types 

 we somehow thought represented stages in evolution. The complex 

 seed-plant had gradually evolved from the simple monad. But the 

 latter was in the habit, at certain periods of its life-history, generally 

 when times were hard, of simply becoming a sporangium, its living 

 cell-content contracting to form spores. Obviously, the sporangium 

 existed long before the leaf. Were we right then in deriving, 

 as our training certainly tended to make us derive, the sporophyll 

 (stamen, or carpel, or what not) from the leaf ? What was faintly 

 foreshadowed in these doubts may become a reality for the next 

 generation of students. There are some who tell us that the sterile 

 tissue which we find forming bands between the spore-producing 

 cells in the sporangium of Isoetes, or segmenting the pollen-sacs of 

 certain seed-plants, recalls the commencement of the evolution of 

 vegetative from reproductive tissue ; and that in such sterile tissue, in 

 fact, we see the origin of the vegetative structure — root, stem, and 

 leaf — of the higher plants. We shall then have at any rate a con- 

 sistent plan of evolution, though one not easily admitting of proof. 



Hydrocyanic Acid in Plants. 



In the Annales du Jardin Botanique de Buitenzovg (vol. xiii., pt. i., 

 1895) appears a most interesting and important paper by Dr. Treub, 

 entitled " Sur la localisation, le transport et le role de I'acide cyanhy- 

 drique dans le Pangimn edule, Reinw." 



This paper seems to throw some light on the steps in the 

 formation of proteid by combination of the substances formed by 

 assimilation in the leaves with substances absorbed by the roots. 

 In Pangium edule large quantities of hydrocyanic acid (HCN) 

 occur, either free or in an unstable combination. The substance 

 obviously is of great importance in the metabolism of the plant, and 

 its occurrence and behaviour have been studied in detail by Dr. Treub. 



