EXPLANATION OF TERMS. 



Abjoint. To joint off or delimit by 

 septa. 



Abjunction of spores. Delimitation by 

 septa of portions of a growing hypha as 

 spores. 



Abscise. To cut off or detach, by solution 

 of a zone of connection. 



Abscision of spores. Detachment of 

 spores from the sporogenous structure by 

 disappearance through disorganisation 

 or otherwise of the connecting zone. 



Abstriction of spores, (a) Delimitation 

 of spores by the formation of septa at 

 the extremity of a growing hypha. A 

 form of abjunction. (b] Detachment of 

 spores from the sporiferous structure, 

 same as abscision. 



Achene. Dry monospermous indehiscent 

 fruit. 



Acrocarpous. In Musci : forms are acro- 

 carpous when archegonia (within which 

 the sporocarp or 'Moss-fruit' is developed) 

 are borne at the extremity of a primary 

 leafy axis the growth of which is thereby 

 arrested. Comp. pleurocarpous. 



Acrogenous. (a) Produced at the summit. 

 (b] Increasing by growth at the summit. 



Acrogynous. In Jungermannieae : forms 

 in which the growth of a shoot is ter- 

 minated by the appearance of archegonia, 

 formed in immediate proximity to the 

 apical cell or from the apical cell itself, 

 are termed by Leitgeb acrogynous. Comp. 

 anacrogynous. 



Acropetal. In the direction of the summit. 

 Comp. basipetal. 



Acroscopic. Loolqng towards the apex, 

 i.e. on the side towards the apex. Comp. 

 basiscopic. 



Actinomorphous. Flowers divisible into 

 similar halves in two or more vertical 

 planes are termed by Braun actinomor- 

 phous. Same as polysymmetrical. 

 Comp. zygomorphous. 



Acyclic. A spiral flower in which the 

 passage from one series of members to 

 the succeeding series, as from calyx 

 to corolla, does not coincide with a cycle 

 of the phyllotaxis is termed by Braun 

 acyclic. Comp. hemicyclic. 



Adhesion. Union of dissimilar parts. 

 Comp. cohesion. 



Adventitious. Produced out of normal 

 and regular order. 



Aecidiospore. Spore formed in an ae- 

 cidium. 



Aecidium. In Uredineae: sporocarp 

 consisting of a cup-shaped envelope 

 (peridium) and a hymenium occupying 

 the bottom of the cup from the basidia 

 of which spores (aecidiospores) are 

 serially and successively abjointed. 



Aethalium. In Myxomycetes : com- 

 pound sporiferous body formed by the 

 coalescence of separate plasmodia. Same 

 as one meaning of syncarp. 



Aggregate fruit. Collection of separate 

 carpels (fruits) produced from one flower 

 i. e. the product of a polycarpellary apo- 

 carpous gynaeceum. Same as one mean- 

 ing of syncarp. 



Amentum. Deciduous spike. Same as 

 catkin. 



Ameristic. In Filices : prothallia are 

 termed ameristic by Prantl which, in 

 consequence of insufficient nourishment, 

 are not fully developed and want the 

 meristem tissue of the cushion from 

 which archegonia are derived, and there- 

 fore have no archegonia, although they 

 have numerous antheridia. 



Amphigastria. InHepaticae: small leaves 

 on the ventral surface of the vegetative 

 body. 



Amphithecium. In Musci : peripheral 

 layer of cells surrounding the endothecium 

 at an early stage in the differentiation of 

 the capsule. 



Amplexicaul. Embracing a stem. 



Amylogenesis. Formation of starch. 



Amylum-body. Spherical or lenticular 

 body in a chlorophyll-band or chlorophyll- 

 plate, which is a centre of starch-formation. 



Amylum-star. In Chara stelligera : tuber- 

 like propagative body densely filled with 

 reserve material consisting of an isolated 

 subterranean node. 



Anacrogynous. In Jungermannieae : forms 

 in which archegonia do not rise either 

 on or very near the apex of a shoot, which 



