436 PLANT MORPHOLOGY 



Gonimoblast. In many red algae, one of the many short filaments arising from the 



fertilized carpogoniiim and giving rise to carpospores. 

 Gullet. A tube leading into the interior of the cell in such organisms as Euglena. 



Haematochrome. An orange-red pigment in the cell sap of certain green algae, such 



as Sphaerdla. 

 Haploid. Having the single or basic chromosome number. 

 Haustorium. In parasitic plants, a specialized outgrowth that serves to absorb food 



from the host. 

 Heterocyst. In certain blue-green algae, an enlarged cell differing from the other cells 



in a filament in being clear, colorless, and thick-walled. 

 Heteroecious. Requiring two different hosts to complete the life cycle, as certain 



rust fungi. 

 Heterogamous. Having a union of unlike gametes, one (the egg) considerably larger 



than the other (the sperm). 

 Heteromorphic. Of unlike form ; a type of alternation of generations in which the 



gametophyte and sporophyte are dissimilar vegetatively. 

 Heterosporous. Producing two kinds of spores, usually of different size, the small 



ones (microspores) producing male and the large ones (megaspores) female 



gametophytes. 

 Heterothallic. Having two kinds of mycelia, distinct physiologically and represent- 

 ing opposite sexes. 

 Heterotrophic. Obtaining nourishment from organic matter, either living or dead, 



as all plants lacking chlorophyll. 

 Histogen. A group of embryonic cells that gives rise to a particular kind of perma- 

 nent tissue. 

 Homosporous. Producing spores of only one kind. 

 Homothallic. Having two kinds of structures representing opposite sexes borne on 



the same mycelium. 

 Hormogonium. In the blue-green algae, a portion of a filament, usually marked off 



by heterocysts, that may become detached and produce a new filament. 

 Host. The organism from which a parasite secures its food. 



Hymenium. In the higher fungi, a layer of cells from which asci or basidia arise. 

 Hypha. One of the filaments comprising the mycelium of a fungus. 

 Hypocotyl. In seed plants, the portion of the stem below the cotyledons in an embryo 



or a seedling. 

 Hypodermal. Situated immediately beneath the epidermis. 

 Hypogynous. With the perianth and stamens attached to the receptacle below the 



ovary and free from it. 



Imbricate. Overlapping in regular order, like shingles on a roof. 



Imperfect flower. Having either stamens or a pistil but not both, these being in sep- 

 arate flowers. 



Indusium. In many ferns, a membrane that covers or invests a sorus. 



Inflorescence. A flower cluster. 



Integument. The covering of an ovule. 



Intercalary. Inserted or occurring between cells or regions of a different kind ; growth 

 occurring between the apex and ba.se. 



Inline. The inner layer of the cell wall of a pollen grain. 



Involucre. In some bryophytes, an envelope partially or completely enclosing a 

 sporophyte and arising from the surrounding tissue of the gametophyte. In 

 angiosperms, a whorl or set of bracts surrounding a flower or flower cluster. 



