Hoya Corona (6) Updated Nov 2018

Hoya Corona

Plant Parts

Six Files

UPDATED:  November 2018

• Part 1:  CLICK HERE

• Part 2:  CLICK HERE
  
• Part 3:  CLICK HERE
  
• Part 4:  CLICK HERE
  
• Part 5:  CLICK HERE
  
• Appendix:  CLICK HERE

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Hoya Leaves (4)

Hoya Leaves

The following mostly consist of leaves I have pressed and dried from plants of my collection. Grown from collected hoya material grown in Fresno, California. In the dried state the nerves are usually more visible. I scanned the leaves top and bottom along with a inch and millimeter scale for comparison.  I have measured the length and widest portion of the leaves, the length and diameter of the petiole and the angle the leaf nerve makes with the midrib.

❦  pg. 1~71, Leaves Top and Bottom  .pdf document 

❦  pg. 1~52, Leaf Data From Hoya Type Descriptions .pdf document 

❦  pg. 1~39, Hoya Leaves from Holotype Sheets: A~M .pdf document 

❦ pg. 40~66, Hoya Leaves from Holotype Sheets: N~W .pdf document 

Also see:  Hoya Foliage - Their Leaves: click here

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Coronal Column Types

Coronal Column Types

 .pdf document

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Tranlator Types Pollinia

Translator types in the Genus Hoya

Pollinia

In attempting to find new relationships of structure in this genus I have attempted to group the translators and the caudicles (two separate structures, one above the other normally) into groups of similar structure. The data was taken from my years of study and accumulation of data on the Pollinaria of this genus.

Structurally I see, without defining the structures too narrowly, that that there are two divisions that can be seen in the translators (1) translators that do not extend out beyond the proximal end of the pollinia (2) those that do extend further outward. The second group (2) can be divided roughly into wide translators and more narrow from the front on view of this structure. Within this later grouping there is considerable variation in shape from long ovals, to drumstick or delta shapes. There is much integration of types. A third category is where the translator extends externally from the side of the retinaculum, Hoya darwinii Loher is prime example. (3) Some I have placed in this group may be due to the pollinium slumping down when removed from the anther pockets for study.

• Part 1, pg 1~17  .pdf document  
• Part 2, pg 1~14  .pdf document  
• Part 3, pg 1~14  .pdf document  

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Genus Hoya: Anther Wings

Genus Hoya

ANTHER WINGS

The anther wings of a hoya are made up the two sides of a channel that extends inward from an area between two adjacent coronal lobes. This channel ends inward just below the stigmatic surface that is situated at the outer corners of the hoya stylar table. It has been assumed this channel is an adaptive structure that aids in the pollination of a hoya flower. The anther wing sides are made of a rigid material, with a rounded edged upper surface, linear in extent, of various thicknesses. Looking at one surface of this structure (by removing an individual coronal lobe and viewing it in side view) it will be observer that the upper edge is thickened (the rounded edge referred to above) and scythe shaped to various degrees, (as in a scythe) the lower portions are thinner, ending below and inwardly as more of a sharp edge. The channel formed by the tow sides form the anther wing, is not always a continuously smooth surface from the outer end inward to its apex, the channel on occasion has a ridge part way up which would hinder the smooth entry of a pollinia if this were an avenue of pollination.

✥ One document: pg 1~9  .pdf document 

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Hoya Foliage: Leaves

Hoya Foliage - Their Leaves

A Pictorial Guide

Hoya leaves are highly variable in size, shape, thickness, texture and venation. They may be glabrous or hairy. The leaf is made up of a petiole and a blade (see labeling on previous page). The blade may have hairs on both surfaces or on only one surface. These hairs are simple or uniseriate. They are thin-walled, very fine, and usually white and vary in length and dispersion. The texture varies from thin e.g. Hoya microphylla, to very thick and succulent e.g. Hoya australis ssp. rupicola, depending on the species and also its habitat. There is usually one or a group of nectariferous glands at the junction of the petiole with the leaf blade.

The leaf surface is covered with a relatively thick wax layer (cuticle) above the single celled epidermis. Below the epidermal layer are palisade cells and below this the spongy parenchyma, throughout which is the scattered vein system. Below then the lower epidermis. In Hoya species the mesophyll varies from undifferentiated to strongly differentiated. There is usually a lot of sclerenchymatous mesophyll fibers, like a mat of tangled spider webs. This later also varies in its presence and thickness among the different species.

It should be mentioned that leaf size shape are the most variable structure of a hoya plant due to environmental factors of light, nutrition, genetics and other factors even in the wild and more so under domestication. Leaves of hoya may have various distinctive markings on the upper leaf surface. This can be spotting, streaks and blotching. This arises from irregular concentrations of chromoplasts (colored cell inclusions) in cells immediately below the upper leaf surface.

• Part 1, pg 1~21  .pdf document 
• Part 2, pg 22~168  .pdf document 
• Part 3, pg 1~37  .pdf document  
• Part 4, pg 1~61  .pdf document  
• Part 5, pg 81~99  .pdf document  

Also See: Hoya Leaves: click here 

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Hoya Pollinaria

Hoya Pollinaria

(2013)

A Photographic Study

This works is dedicated to the serious student and researcher who wishes to learn more of the Genus Hoya. It is hopped it may lend additional data for pollen researchers in other Asclepiad genera and species. Mostly it is in appreciation of the intricacies of any study and the realization that no subject is simple once an in-depth inquiry is started. I wish to again thank all who have contributed of material and time to further my work in this field, their concern and helpful criticism is always appreciated.

“The pollen masses present great variations 

in size, form, and length of pedicels 

and probably afford excellent characters”
J. D. Hooker 1838 in Flora of British India.

• Part I:  TABLE OF CONTENTS  .pdf document (pg 1~101)
• Part II:   .pdf document  (pg 102~205)
• Part III:  .pdf document   (pg 206~304)
• Part IV:  .pdf document  (pg 305~404)
• Part V:   .pdf document  (pg 405~507)
• Part VI:   .pdf document   (pg 508~598)
• Part VII:   .pdf document  (pg 599 ~ 660)

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